Service-Oriented Architecture (SOA) is intended for the integration of heterogeneous applications. Complex business processes are composed by a group of specific Web services using WS-BPEL (Business Process Execution Language), and these Web services may be designed by the enterprise itself or third-party services providers. Today there are many WS-BPEL engines that support the deployment and execution of WS-BPEL files. However, the WS-BPEL activities have to be pre-defined, and if at runtime a Web service call fails, the entire business process is pronounced to be failed, thereby jeopardizing the reliability of SOA. Although the WS- BPEL supports compensation mechanism, it is complex and not flexible. In this work, we propose a process design model to support dynamic Web services selection that eases the designer¡¦s job. This model has been implemented, and the prototype is evaluated to demonstrate that it indeed improves the overall business process reliability.