The generation of assembly precedence constraint is the key step of assembly planning and the most difficult one as well. In this paper, the implementations of some methods of generation of assembly precedence constraint are presented at first. The advantages and disadvantages of these methods are discussed as well. Then, one method which combines the knowledge of geometry and assembly experience is presented. By using the method, the assembly knowledge base and database are established. Several feasible solutions are provided at the same time. Finally, a conclusion is reached. The advantages of the method and suggestions on further research are provided as well.