This article is mainly about the problem of interoperability between the Workflow Management System and the legacy systems which have different architectures. The way of building a communication adapter in the Workflow Management System can solve the problem of interoperability between the two types of systems as mentioned above. In this article, we will introduce the overall structure of the communication adapter in details, and we also will talk about the communication adapter's basic functions and how to implement it. And finally, base on the Web Service, We implment and deploy the communication adapter actually, by packaging the functions of the Workflow Management System and the legacy system as the Web services to solve the problem of interoperability.