Abstarct: One of the basic requirements for populated cities is high quality public transportation. Subway are very popular because of efficiency in time and cost and ease of use. Subway ventilation systems in the operation time is more important than drilling time and Should be designed to provide the air conditioning for the passengers and staff. CFD modeling helps us to find out the amount of air required and number of fans for ventilations of environment. In this research CFD modeling and parametric study was used to determine the volumetric flow rate and number of fans. ANSYS Workbench software used for modeling and solving. finite volume modeling was used for CFD modeling and for turbulence model standard k-ε was used. Given that the first phase Mashhad subway includes six stations and these stations is similar, only one model was built and the results used for all stations. using Airwasher and its impacts on air conditioning in summer was studied using CFD and finally, strategies was presented according to the weather conditions in the Mashhad city for efficient use of the subway system. The model was validated with two different methods. Model was compared with the plan Zitron company. Results indicate that the volume flow rate designed by the CFD model is Equal with volume flow rate fan made by Zitron company. For checking the speed and temperature and compare it with the CFD model VANE Anemometer Barometer Humidity/Temp device was used.