This paper is focused on using the method of computer technology combined with the knowledge of experts to determine heavy-duty cutting processing parameters according to the relevant theories of metal cutting. This “Expert System of the Parameter Optimization in the Heavy-duty Cutting Processing” is based on the VC++6.0 programming language and SQL Sever 2000. It is divided into two subsystems, turning and milling machining. Taking the turning machining subsystem for example, by using methods of generating expression combined with frame representation, this paper classifies and generalizes related knowledge, and combines the knowledge base with the data base to set up the knowledge base of the subsystem. Also this paper introduces the process of inferential mechanism of the optimizing modules of cutters and machining engagements.