Abstract: The flexible assembly and its assembly sequence are a very important research and application area in the CAM and CIMS. Based on the knowledge representation and the technique of expert system, some representations of the assembly sequences have been mentioned, and a prototype of the flexible assembly planner and its computer simulation for an assembly sequence of a typical mechanism have been proposed. The approach proposed in this paper can be generalized to more complex assembly work, and put forward some new requirment for the control and the programming of the CAM and CIMS.