Lots of collaborative works are developed by workflow at present. The modeling of workflow is mainly by Petri Net. This paper studies the test coverage of collaborative workflow system to improve the system quality. By analyzing many Petri-Net models, the paper puts forward generic advance Petri Net model. And other workflow Petri Net models can be compatible with the generic Petri Net. Then test coverage strategy is considered and test case is designed according to the strategy. This method not only can meet the requirement of test coverage, but also can assist test case design and further execution of test case. Finally, a typical example is introduced to illustrate effectiveness of this method in collaborative workflow application.