A newframework of the Environmental Control System( ECS) has been put forward in which the interchange of energy between the air conditioning system and the liquid cooling system is established by the air-liquid heat exchanger. This framework can raise the capacity usage ratio by reducing the thermal load of the liquid cooling system meanwhile reducing the quantity demanded of the bleed air for the air conditioning system. A simulation is conducted by the software named AMESim to calculate the performance parameter of this framework of ECS in four typical working conditions,and the efficiency of the air-liquid heat exchanger,the key parameter of this framework is optimized in order to reach the goal of causing the minimum aircraft performance penalty. The result of the simulation and the optimization shows that the newframework of ECS can reduce the aircraft performance penalty obviously comparing with the traditional framework. The aircraft performance penalty decreases first and then increases with the efficiency of the air-liquid heat exchanger increasing invariably. It means that the efficiency of the air-liquid heat exchanger has an optimal value for the newframework of ECS.