In this investigation, behaviour of airflow inside an electrostatic precipitator with three different distribution plates has been considered by means of numerical & experimental methods and results , have been compared together. This device has been designed &produced in this center for the first time in Iran, and its ability to absorb particles, haze and soot is good. But for increasing the efficiency there must be some changes to on miscellaneous sections. Therefore, here we consider the effect of distribution plates to increase performance, because when distribution flow at cross sections of precipitator is uniform, the efficiency will increase. To have a numerical simulation, fluent software version 5.3 was used, and for modeling turbulence the RNG k- e turbulent model applied. This program after discretization governing equations on a body fitted coordinate system, that is produced in preprocessor, integrates this equations on control volumes and determines the rate of quantities on control volume faces using order two (upwind) approximations. Finally by means of a Pitot tube velocity magnitude of fluid in two sections of domain was measured & compared with numerical results which shows a good agreement. After simulation the three model, e.g. without distribution plate, with a distribution plate after inlet duct and with two distribution plates (once after inlet duct and other before outlet duct), and taking some results and by comparing them, we conclude that the use of combined distribution plate can give a good result.