To improve the Web system performance, Web which works under the offline state is studied. Based on the features of Isolated Storage, the solution of using the Isolated Storage in a Web commercial system is presented. A local smallscale database management component is designed with the Isolated Storage APIs, and the management of the local data storage is solved. Meanwhile, the local data synchronized with the remote data is achieved based on the incremental updating of the data synchronization engine, which uses the TCP socket communications. The socket service is designed to achieve the clientserver time synchronization and push data to the client from the server. The experimental results show that, this system runs well in a low bandwidth or network fault state, and the reliability of the Web systems is improved.