Although there can be some value in accessing a single Web service, the greater value is derived from assembling Web services into more powerful composite Web services. Web service flows are composite Web services based on process. The Web service flows specified by current specifications are static that can not dynamically adapt themselves to often changing business environment and have the problem of code scattering and tangling relating to crosscutting concerns that cut across the process boundaries. In this paper, we apply AOP concept to support the dynamic adaptation of Web service flows. We give our approach for describing aspect as extension to BPEL, considering how to reuse the definition of an advice that maybe has different type at different pointcuts. And we present an approach for verifying the correctness of the web service flows weaved with aspects before they are deployed.