In this study, we developed an expert system for designing of frame work of Removable Partial Denture by the method of Artificial Intelligence. Both of Quick Basic and Tuber C language are used in this program. This system consider more other relative factors in removable partial denture designing except the amount and position of missing teeth. Base the idea of multy-layer knowledge we divide the process RPD designing into different layers according to their logical relationships. So, this system could imitate better the expert of prosthedontics to do the clinical examination, diagnosis, treatment plan and denture designing. There are 11 modules in this system totally. They are used to accomplish the case register, first visit examination, treatment plan, abutment examination, denture designing, biomechanic analysis of abutment, reference, explanation and etc. We used this system for 20 partial edentulous patients and compared the results with the designing plans of expert of prosthedontics, the rate of conformity is 83.6%.