This paper presents the design and implementation of Distributed Object-oriented Web-based Simulation (DOWS). DOWS is an object-oriented simulation system based on a new concept, a director-actor model. It also models a distributed simulation as a collection of actor objects running concurrently at different nodes. DOWS is implemented using Java objects which interact with each other through Java RMI. Each director object is implemented as web client which downloads and executes the proper applet from a HTTP server, and hence DOWS provides a web-enabled simulation environment which allows users to easily instantiate the simulation model using the HTTP server. The whole simulation can be speed up by decomposing the simulation model into several submodels and mapping them onto the actors. DOWS also provides an efficient virtual real time simulation environment which integrates the coordination among actors by supporting time synchronization, simulation message transfer, and network fault detection.