Abstract: The present invention relates to a software system performing direct simulation of workflow process definition model following WFMC (Workflow Management Coalition) within workflow system (engine). The simulation system comprises 1) a global clock for simulation time management, 2) participant simulators receiving work item from workflow system (engine) and starts/terminates the work item, 3) a human participant interface for the direct participation of human in simulation, and 4) a supervisor processing input information required for performing simulation. With attaching the simulation system of the present invention to existing legacy workflow system (engine), and executing predefined process definition model, automatic simulation can be performed, which is called as autonomous simulation. Moreover, the present simulation system also supports constructive simulation mode which directly makes human perform the roles of some participant simulators.