Service-Oriented Computing (SOC) and Service-Oriented Architecture (SOA) provide a paradigm for creating composite service with distributed web services over the Internet. Through the integration and coordination of distributed web Services, Web Service Business Process Execution Language (BPEL) can deploy a composite service rapidly. However, in a complex dynamic network environment, it is difficult to guarantee the reliability of BPEL application. To verify the reliability of the BPEL process, this paper proposes a method which can extract the model from a BPEL process and analyze it through probabilistic model checking with Prism model checker. During the extension process, we add reliability attribute to each invoked sub-services. By structure extraction, the BPEL process is transformed to a PLTS system. Then, we generate a suitable analysis Markov model according to the feature of the PLTS model. Finally, we use PCTL formula to describe the properties of the system, and check it with Prism tool.