Abstract: This paper establishes models of the VRV & fresh air conditioning system and the primary return air conditioning system by using the software of Airpak, to simulate the temperature field and velocity field distribution of indoor air flow under two conditions in summer, and then to evaluate indoor thermal comfort and air quality by adopting the indexes like PMV-PPD and air age. Results show that both the wind speed of two schemes can meet the requirements of comfort air conditioning, without obvious sense of blowing for people. Compared with the VRV & fresh air conditioning system, the primary return air conditioning system has smaller air flow disturbance, smaller temperature fluctuation in respiratory area, and better indoor air quality with timely delivered fresh air.