The airborne pod is a kind of airborne optical-electronic detection and countermeasure equipment, which can observably improve the airplanes operational performance in combat.The environmental control system is an important part of the pod, which design is difficult and very important for the pod design.A method for working performance analysis of the environmental control system was presented.Acoording to the method, we obtained the formula for calculating the temperature difference between inside and outside of the pod, and that for calculating the mininum and the maximum speed permissible for different altitudes.This method was certified by theoretic analysis and simulation with an example of an optical-electronic pod, which can be taken as a good reference for the design of an environmental control system.