In this paper module of a product is determined by the characteristics of a product itself and process. To analyze the characteristics of the product information on subassemblies and parts can be obtained by analyzing the existing product. Based on the analysis of characteristics of product structure and function determination rules of a module degree could be proposed for assembly and disassembly process and product structure and function. By applying these rules of a module, module of a product is classified into full half and non-module depending on the module degree of a product. As a result of module degree analysis simpler assembly process and reduced structural interference can be realized. For the product function simpler updated and multi function can be also achieved.