With the fast development of Internet, chatting room has become the most widely used communication tool. A kind of multi-functions network chat system based on open stream media server Red5 is proposed in this paper. Since the same registered users of different websites usually use the fixed user names and passwords, the vulnerability of these fixed passwords exist, which could be solved through dynamic Hash authentication based on target site URL, random number and password. JavaScript, Flex, AS3 and JSP technology are used for development and are combined with the popular Struts2, Hibernate and Spring framework. Hence, functions such as real-time video or audio chat, MOD and file transfer could be realized. Test results show that this system could be proper used in the actual network environment, and the performance on Safety, efficiency, maintainability and expandability is also very excellent.