Abstract: Electronic pods are widely applied in modern fighters to promote performances of electronic countermeasures， reconnaissance， navigation and guidance. The turbine environmental control system using ram air as cold source is capable of providing sufficient cooling power for the pod， and keeping the pod operating safely and efficiently. TTC turbo cooler with expansion turbine， powered turbine， and compressor turbine is the core component of environmental control system. This paper analyzed different environmental control systems， conducted numerical solution of expansion process and compression process in the corresponding impellers， aiming at the coupling feature of three-wheel system in the TTC turbo cooler. The coupling model was established and verified by theoretical simulation experiments according to the solution results. The complex nonlinear coupling relationship between the parameters was ultimately quantified based on the numerical calculation results.