In order to guide the design of the auxiliary cooling system, a steadystate simulation model of the auxiliary cooling system forairlinerconsisting of airborne vapor cycle and liquid coolingcylce was developed.The component model of compressor, heat exchanger and electronic expansion valve suitable for system simulation was established; the relationships among the the units of the system were analyzed and decoupled, and an appropriate system solving algorithm is established among. The performance of the system with the variation of refrigerant change was predicted and analyzed. The analysis results show that the prediction of the auxiliary coolingsystem performance accords with the theoretical analysis results by the steadystate simulation model of the auxiliary cooling system,and the model is reliable.