In economic studies of industrial and mine projects, there are many factors as uncertain variables related to the future (sales, demand, net present value and etc). Therefore, such studies should be carried out based on forecasting. To obtain reliable results in these situations, we should use risk analysis methods. One of these uncertainty methods is to employ models to be simulated.One of the methods that can be use in these models is Mont Carlo simulation, in which, some factors as random variables will be studied for the future. Future prediction of each random variable is assessed considering a probability distribution function. The aim of this research work are to describe Mont Carlo simulation and its application in risk and decision management of evaluation industrial and mine investment project and forecast probability economic conditions. The result of this study indicate that: in economic study of each investment project, first, we should recognize the uncertainty variables and distribution function of them, and then with replacing the distribution functions in appropriate cell of financial model of the project, forecasting of future using Mont Carlo simulation and evaluation of risk can be done.