For the development of the commercial aircraft environment control system (ECS),with the thermodynamics theory,established mathematical models of the recirculation system and the simulation software has been developed. Using this simulation,analyzed the impact of the recirculation to the steady and dynamic performances of air conditioning system. Then the design principle and parameters scope of the recirculation system are concluded.The analysis result is directly applied to design the ECS of the certain commercial aircraft,the good achievement is gotten.