Introduction: Broccoli is a rich source of minerals such as potassium, phosphorus, calcium and sodium. Additionally, broccoli provides vitamins, especially vitamin C, vitamin A and folic acid. In addition, it has been reported as a one of the main sources of natural antioxidants such as phenolic compounds, glucosinolates and isothiocyanates. Because of the high corruptibility of broccoli, it is very important to keep its effective components as much as possible. Drying is the most common method for enhance the shelf life of food products. The foam mat drying method was developed in the 1960s. This method involves mixing pulp or fruit and vegetable juices with a foaming agent and a foam stabilizer to prepare a stable foam that is spread and dried on a tray, then the dried product is ground to a powdered product. In this technique, due to increasing of the material area, the drying rate is high. Convective hot air is generally chosen as the drying medium of the foam mat method. The disadvantage of this drying method is the poor heat transfer of the air around the foam. Microwave heating, with its ability to produce volumetric heat inside the material, can overcome this limitation. Microwave energy can penetrate directly into the foamed pulp to evaporate moisture inside the foam,continuously generated vapors stimulate foam bubbles, which expand the evaporation level and speed up the drying process even more. There are many strategies to improve the quality of microwave-dried products, such as combining microwave and convective hot air, intermittent drying, and microwave-vacuum drying. The combination of microwave and convective hot air has been used successfully for a number of agricultural products such as garlic, grapes, carrots, kiwis and blueberries. The combination of these two methods has a shorter drying time than single convective hot air, and the final sample will have higher quality. Material and methods: Broccoli was purchased from the local market of Tabriz and its enzymes were inactivated by blanching in 90°, C hot water for 4 minutes and then immediately cooled in ice water for 5 minutes. It was then pulped and stored in a freezer at minus 18°, C until drying experiments were performed. Broccoli pulp was first thawed before drying experiments. 3% (w/w) egg white as foaming agent and 0. 5% (w/w) methyl cellulose solution as stabilizer agent were used to prepare the broccoli foam. The foam was spread to a thickness of 5 mm on a glass plate and then it was dried with different drying methods including convective hot air (at 40°, C and air velocity of 1m/s), microwave (90w) and combination of microwave and convection as pre and post treatment (MWCHA and CHA-MW). The moisture content of samples was measured at 10 minute intervals (in CHA method) and at 2 minute intervals (in MW method), and the drying process was terminated when moisture content of the samples reached 0. 04 g water/g dry solids. The produced powders were then scratched off by a special spatula and were immediately ground in a crucible in order to prevent further moisture absorption and kept in the refrigerator until further testing. Results and discussion: The combination of microwave and convective hot air (in both pre and post treatment) compared to microwave method, had lower effective moisture diffusivity coefficient and drying rate but higher energy consumption. The average of moisture content and moisture ratio was also affected by drying method and the combination of microwave and convective hot air (MW-CHA and CHA-MW). In MW-CHA, the average of moisture content and moisture ratio was higher than MW and CHA drying method, but in CHA-MW, the average of moisture content and the moisture ratio was the lowest obtained. Among the four drying methods, the hot air drying method had the lowest drying rate due to the hardening of the surface due to the loss of surface moisture. This phenomenon slows down the exit of moisture from the product and reduces the drying speed. In the microwave method, in the early stages of drying, the samples have high humidity. High humidity is the main reason for volumetric heating in the microwave method, in that bipolar molecules absorb a significant part of the microwave energy and lead to an increase in product temperature and rapid transfer of moisture to the surface. The flow of water vapor from the inner parts to the surface of the product creates a porous structure, resulting in faster evaporation of moisture, and ultimately increases the drying speed. Therefore, the highest drying rate was observed in the microwave drying method. The passage of time and the reduction of moisture in the product reduce the absorption of microwave power and, as the drying process progresses, leads to a slowdown in the drying speed. Compared to the combined drying methods, due to the prevention of surface drying in the microwave-hot air (MWCHA) method, this method had a higher drying rate than the hot air-microwave (CHA-MW) method and hot air alone. The mean drying time were from low to high: microwave (48 minutes), hot airmicrowave (70 minutes), microwave-hot air (102. 16 minutes) and hot air (120 minutes), respectively. The effective moisture diffusion coefficient of all four drying methods was significantly different from each other at the level of 5% probability and were from high to low related to microwave, hot air-microwave, microwave-hot air and hot air, respectively. The high effective diffusion coefficient of moisture in microwave drying is related to its volumetric heating mechanism. In a microwave field, the core temperature of the product rises, creating a pressure difference between the core and the surface of the product (Junkoria et al. 2017), creating a more porous structure and more vapor permeability, and ultimately increasing the effective moisture diffusion coefficient due to faster heating. (Dehghani Khiavi et al. 1399). Hot air method has the lowest effective moisture diffusion coefficient value, due to the low air temperature (40°, C), because there is a direct relationship between the effective diffusion coefficient of humidity and temperature, and on the other hand, the hot air energy for moisture exit is lower than other methods, so the effective moisture diffusion coefficient in this method is at its lowest value compared to other drying methods, and this is the reason for the slower drying speed in this method. In the combination of hot air and microwave, when hot air (as a pre-treatment) is applied at the beginning of the process, the drying and dehumidification process is controlled by the microwave and the effective moisture diffusion coefficient in this method are higher than hot air. When hot air is applied at the end of the process (as a post-treatment), the drying process is controlled by hot air and the effective moisture diffusion coefficient are lower than hot airmicrowave, but higher than hot air alone. Conclusion: According to the least energy consumption, drying time, moisture content, moisture ratio and the most effective moisture diffusivity coefficient and drying rate, MW and CHA-MW were the optimum methods for drying the broccoli foam (with 0. 88 and 0. 7 desirability, respectively). The use of microwave energy as a pretreatment for hot air (CHA-MW) was able to significantly reduce the average moisture content and moisture ratio compared to the microwave method alone, and produce a powder with lower moisture content and longer shelf life.