Workflow management system is playing more and more significant role in business process management (BPM) and office automation (OA) of enterprises[. It can improve the efficiency and manageability of an enterprises daily teamwork, control as well as coordinate the processes[. Traditionally, it is not easy for the workflow modeling method to describe the complex business process clearly and intuitively. In this paper we improved the role based workflow model, and proposed a workflow modeling method based on multi-role playing. It is possible to make the modeling easier and simpler when we come to the complex business process modeling problems. Finally, an example of a B/S based Enterprise Financial Reimbursement Management System (EFRMS) is demonstrated to prove the convenience and feasibility about the method mentioned.