With the times progress, much expertise which apply into the Expert System transform to cope with the background of different times. Consequently, the Inference Engine and Knowledge Base in Expert System need to do some timely adjust and increase. However, specialists who possess expertise are incapable of altering the design of the Inference Engine. Therefore, the thesis tries to do more effective combination between the Inference Engine in Expert System and the miscellaneous expertise which alters with the times change through modularizing the interface and Inference Engine after building the Expert system. It offers specialists a better and more rapid assist for them to increase and maintain the expertise in Expert System. Furthermore, it assists the developers to renew the system more efficiently with lower capitalized cost and makes the system to be more flexibly as well.