In view of the Fuzziness and the uncertainty of the expert knowledge of the fault diagnosis expert system，this paper presents a method of Fuzzy production rule (FPR)knowledge representation by using Fuzzy Petri nets(FPN)model，knowledge store and Fuzzy reasoning mechanism，and gives the algorithm implementation. Furthermore，taking the fault diagnosis expert system for the JCS-020 (FANUC) manufacturing center as an example，We have proved in this paper the feasibility and validity of the method.