Abstract: T/R modules and their power supplies are the main heat sources in the active phased array antennas, the effective heat dissipation way of which is liquid cooling or air cooling. In the active phased array antennas adopting liquid cooling, besides the T/R modules and the power supplies, the modules with low power loss located separately such as cell controllers, high frequency receivers and power divider networks also require corresponding heat-dissipation systems called environmental control systems. In this paper, the middle layers of left and right sandwich beams in the antenna structure frames are considered as static pressure cavity for air supply and air returning cavity respectively. Based on the air supply principles of the whole pore-plate, the opening sizes and quantities on the side plate of left sandwich beam are worked out, and then the environmental control system design is accomplished with reasonable planning of the air flow path. Detailed parametric simulations of the heat-dissipation model based on an active phased antenna are performed. According to the simulation result, combined with practice, the surface temperature distribution of the modules with low power loss in the antenna structure frames is obtained. The results clearly demonstrate that the highest temperatures of above heat sources satisfy the operation requirements，which proves the feasibility and reasonability of the design method of this environmental control system.