In intercity vehicle, the air conditioning and ventilation system has an important impact on breeze speed, temperature and humidity of which directly affects the thermal comfort of passengers. The three-dimensional full flow field geometric model of the air conditioning and ventilation system in the passenger compartment of an intercity vehicle was established. By combining SIMPLE algorithm with the Realizable ,k,-,ε, turbulence model, and adopting the flow inlet and outlet boundary, the simulation calculation of the full flow field in the passenger compartment of the whole vehicle was completed. The accuracy of the simulation results was verified by the test, and the flow field distribution, breeze speed, speed field and temperature field in the passenger compartment were further analyzed. The results showed that the distribution of flow field and temperature field in the passenger compartment of the whole vehicle was even, which met the requirements of engineering design.