In this paper, a novel multimedia transmission server system is designed using rule-based expert system technology. Working parameters and session management methods are separated from the decisionmaking procedure and stored in a knowledge base (XML format). The server fires different transmission strategies inside the knowledge base by runtime inference. Thus it can easily adjust transmission parameters under various environments and incorporate newly developed methods without significantly changing the main body of the server code. Results indicate that the expert system can efficiently deliver smooth streams and save server resources. The overhead brought along with the flexibility is tested to be acceptable.