Process interoperability is important to achieve collaborative product design across enterprise boundaries. In this paper, first analyzes interoperability requirements in collaborative design process. Then the Process Specification Language (PSL) is introduced to design process modeling and PSL description method of design process information is given. In the end, a process interoperability framework is established based on PSL ontology and main function of modules are discussed. The framework provides an effective solution for information exchange and sharing among different process management systems in collaborative product design.