Focusing on the issues that it is very difficult to test the parallel software system, and the size of state space is too large, a Colored Petri Net (CPN) model for simplifying the tested behavior of the parallel model was proposed. Firstly, the original model was divided into several sub modules according to the number of the special nodes, such as concurrent transitions, synchronous transitions, the branch places, and the confluence places. Secondly, the position of the tested behavior and the test set was created. Finally, the execution priority was set for the non-test behavior in each parallel module which met the reduction condition. By comparing the results of the state space analysis before and after simplification, the reduction rate of nodes in state space is at least 40%, and the full coverage test path generated by the tested behavior was not affected by the simplification.