Abstract: In order to decrease the air condition energy consumption of high and large-space building such as theatre and stadium,this paper puts forward an integrated system of tunnel and solar wind tower for the passie cooling system of a theater in Hainan. In this system,the outdoor air is cooled by tunnel heat exchanger and powered by the strong buoyancy generated by the thermal pressure enhanced by the solar wind tower,which can eliminate the surplus heat in the theatre by natural ventilation. Effect of tunnel length on ventilation performance of the integrated system is simulated by software of FLUENT. The results show that the air supply temperature is reduced by 2 ℃,which improves the comfort of the working area,while the air flow rate is reduced by 17 % when the length of the tunnel is increased from 80 m to 140 m for the single tunnel integrated system. The temperature and velocity at back row seats are exceed and approximate the upper limit when the length of the tunnel is 80 m and 100 m. Compared with the single tunnel integrated system,in order to attain the same supply temperature,the double tunnel length can be decreased greatly and the temperature and velocity are more uniform.