Integrated process planning and scheduling (IPPS) is a good way to achieve a global improvement for the performance of a manufacturing system, it has been extensively researched over the past years and it continues to attract the interest of both academic researchers and practitioners. This paper first summarizes the critical problems of IPPS and then a survey of the integrated model and optimal implementation method for IPPS is presented. The integrated model is categorized into interface-oriented integration and function-oriented integration two types based on the integration object and are discussed in detail respectively. The deficiencies of the current integrated models and the suggestion for further improvement are also given. The integration of process planning and scheduling has been implemented by variety methods and agent-based approach is discussed in more detail. Finally, future research directions and conclusions in IPPS research are discussed.