Web service is a key distributed computing technology to achieve "software as a service" (SaaS) in cloud computing. How to integrate various web services according to business processes correctly and efficiently, realize the seamless integration of services, and form enterprise level service processes with abundant functions has become an important problem. In this paper, we presented a new web services composition model and its verification algorithm based on interface automata. By extending interface automata, this model supports semantic descriptions of web services. We proposed the transformation rules and transformation algorithm between BPEL and the semantic service interface automata model. Furthermore, an interface automata composition algorithm was designed to achieve the concurrent composition of interface automata. In order to judge whether the service process generated satisfies the business function requirements, a verification algorithm was designed to validate the execution sequence of the concurrent composite interface automaton, and the simulation experiment showed that verification algorithm could be used to validate the consistency of the service process and the business process correctly and effectively.