Hohhot hydropower station is being built from the year of 2007. There are many complicated heating facilities and equipment in the powerhouse, such as electricity generators and transformer. The air distribution of the powerhouse is affected by the complex heat sources. In this paper the model size is 1/50 of the real scale and 2D-PIV is used to study the air distribution in the model of large underground space. The supply outlet is located on the roof and the heat source is located on the floor. The different supply air conditions and heat release rate are discussed. Three air supply are discussed: v/v(0) = 0.75, v/v(0) = 1, v/v(0) = 1.25 (v(0) is designed air supply speed, v(0) = 0.94 m/s). And we also carry out three heat release rates: Q/Q(0) = 0.75. Q/Q(0) = 1. Q/Q(0) = 1.25 (Q(0) is designed heat release rate, Q(0) = 7.12 W). The results show that the supply air velocity has a remarkable effect on air distribution characteristics of the large space and occupant zone velocity. However, it is also observed that the heat release rate has little effect on air distribution of large space and occupant zone velocity. The air supply velocity and the air inlet location should be paid more attention in designing air distribution. The experimental findings are useful for optimizing the design of air distribution in a large space with complex heat sources. (C) 2009 Elsevier Ltd. All rights reserved.