In this paper, we firstly discuss the necessity of a sirnulation tool which can handle a large and complex manufacturing system under CIM environment, and then consider problems itlcurred by developing such a large system model. A distributed simulation model developed on a distributed computer system is then shown to be a promising method to cope with the problems. Lastly, a time bucket method with time warp mechanism is proposed for the synchronization of the distributed simulation and its computational features are investigated by modeling a virtual factory on six workstations connected by the ethernet.