Nowadays, workflow technology has been intensively applied in the domains of administration, production, and scientific research. For the complexity and variability of process logic, how to build a well-structured business process is a practical problem. Thus, process model analysis and improvement become one of research directions in workflow technology. Firstly, according to the modified workflow process meta-model, a P/T system based workflow model procedure net is proposed. And then, a set of simplification rules are given to verify two structural conflicts of the process model, i.e. deadlock and lack of synchronization. Finally, following these rules, a procedure net example transformed from a business process is simplified, and the result is obtained.