Business processes present business logic of enterprises and or web services. In current Internet based dynamic business environment, business logic and resource allocation may have to change more frequently than before to match various business conditions in time. Business process deployment is a very costly procedure. It is desirable that a business process reengineering action could be verified before it is deployed. In this paper, we present an innovative business process simulation system that can use historical execution information of business processes when it is available as reference to set up simulation conditions. Integrated with a process modeling facility, this simulation system allows business processes to be simulated before they are deployed. 5 Pages