The structure of the test system gets more complicated, the test tasks increases in number, and the relations between them are stronger. So, the traditional establish method of the test system relying on people's experiences does not meet the needs. Then in the process of test system's design, a new modeling and performance evaluation method based on the generalized coloured stochastic Petri net (GCSPN) is used in the article. For example in the design of the radar automatic test system, the system structure, test resources and test function are firstly analyzed, then the GCSPN model of the system is built. The model needs to be made simple and decomposed on the rules. Moreover the system's resource utilization and test time are evaluated on the stochastic Petri net. At last, the radar test system is built up referring to the Petri net model. The system runs normally, and the test values are almost consistent with the evaluations. It is compared with the parallel system designed by TestStand software. The result embodies the advantages of the GCSPN modeling method.