Component-Based development method is thought to be the latest outcome to tackle software crisis, but in practice it didn抰 reach the expectation. The methodology of component design is not perfect due to the lack of explicit guidance to build the practical application. In this paper, a business component design method is given, which uses the Cluster Algorithm to identify two kinds of business components (process component and entity component) and takes the requirement models as the data source of Cluster Algorithm samples. Several formulations are also given to calculate the value of samples?relationship. 揅ore Entity?was chosen to achieve better accuracy of Business Component identification, and granularity formulation is given to reduce the complexity of Business Component. The design steps of Business Component Interface are described at last.