The computational fluid dynamics (CFD) and measurement technique were used to simulate and analyze the indoor airflow field in isothermal air-conditioned space of a gymnasium. Some different airflow patterns according to different supply air were simulated by numerical methods. The authors set up the full-scale experimental study of the airflow pattern of the same gymnasium. Measurement data and analysis of air distribution were presented in which the airflow is isothermal. Based on comparison with measured and simulated data, the airflow pattern of the sports hall is analyzed, and the results show that the numerical simulation in gymnasium and the similar large space buildings is qualitative correct because of the complicated boundary condition.