This paper mainly studies T/R (Transmitter and Receiver) module in radar and its internal solid-state microwave power device, and the mechanisms of performance parameters' change affected by temperature. First, we establish a compact model of solid state microwave power FET (Field Effect Transistor). Second, based on the compact model, a behavioral model of T/R module is developed. By simulating the behavioral model, trends of performance parameters of T/R module under varied temperature conditions can be analyzed. Last, we conduct a series of experiments to verify the behavioral model. Above all, our study aims to provide a reference for the design, analysis and operational reliability of T/R module.