Web Services can help business processes integration (BPI) in both flexible and efficient manner to fulfill dynamic business demands and trustworthiness will become the critical concern for realizing the vision of such service-oriented enterprises. In this paper, we propose a trustworthy Web Services framework for BPI to discuss various trustworthy issues from three different perspectives: structure, service and management. From structure perspective, we consider that the dependability of underlying data, applications and organizational policies are the basis of the trustworthiness of Web Services based BPI. From service perspective, each involved actor in the business process model should be described by both functional and trustworthy capabilities so that business analysts could aggregate qualified Web Services to fulfill the business goal. From management perspective, enterprises can perform the evaluation of quantifiable attributes of executed Web Services to manage trust relationships among partners and customers. The proposed framework will not only assist enterprises perform Web Services based BPI in a trustworthy way but also facilitate enterprises to develop trustworthy Web Services.