Abstract: Reference elements, assembly modes and assembly relations between components in the assembly process are studied and summarized to three assembly types. A generalized assembly modeling concept including decision making of design methodology and gathering the product social attributes information is presented for carrying out cooperative assembly planning activities. Accordingly, an information model adapting to cooperative assembly is set up by introducing the notions of assembly knot of implied constraints, and assembly link to indexing the involved components, thus a comprehensive product assembly relation graph is established by means of searching the above assembly model. After classifying the assembly link into hierarchical levels according to the decoupling principle, hierarchical assembly graph presented in the form of concentric circles is formed, which in turn provides a straightforward way for planning the product assembly sequence.