Abstract: In order to solve the problem of establishing general multimedia platform brought by complexity of multimedia technology and heterogeneous environment, Web Service is used to establish loosely-coupled web-based distributed multimedia platform that can operate across all major operating systems and programming languages, and includes H. 264 encoder service and content-based image retrieval service. The platform's architecture, advantages and the method of establishing such a platform are also detailedly introduced. Common application servers are used in the server end to deploy a H. 264 encoding service and an image match service based on image color and spatial information. Traditional windows GUT application, web browser and embeded platform simulator are used at client end.