A system model for web deployment of 3D terrain which mode is Browser/Server based on J2EE tri-tier system framework is given in the paper. Technology of Applet, JSP, Servlet, Java3D and BC4J has been integrated in the model. The main idea of this model as follows, using Java3d to develop the Applet that can interact with user, and the Applet embeds in web page of JSP. The Applet applies agent server, BC4J to communicate with server of Oracle database. The experiment shows that this model has some certain superiority.