A service broker supporting customers plays an important role in internet marketplaces. Recently. several intelligent brothers have been developed for electronic commerce, outline shopping mall, and electronic marketplaces. While these systems provide interesting shopping experiences, they fall short in fully exploiting the capabilities, such as the service integration and automatic execution required by internet market places. In this respect, we propose a workflow-based service broker system. Dependent services in our approach are modeled as workflow processes, which are automatical1y processed by a workflow engine. In the proposed system all data exchanges are realized through XML providing platform independent, extensible, open. and interoperable architecture.