In order to migrate the enterprise legacy system to the web, a multi-agent based legacy system encapsulation model is proposed.  Firstly, the characteristics of legacy system are analyzed, and then the data and functions that need to be published are confirmed. Secondly the legacy system is wrapped into web components with common interface, and these components are managed by the application server. Thirdly, the clients can send requests to the application server, and receive the return result from the application server.  Due to adoption of wrapping technology for legacy system, original security and stability of legacy system are guaranteed in the web components. Finally, the validity and practicability of the migration technology are verified through the application in the encapsulation of Matlab as web components.