Abstract: The 3D assembly process in the form of animation, audio and text, expresses the assembly process and assembly requirements vividly. As a result, workers could easily understand and improve the quality of assembly, and the information is not ambiguous. This paper studies focuses on how to use the information in the 3D model to complete the 3D assembly process effectively. Firstly, basing on the studies about MBD technologies, it establishes the MBD-based assembly information model. Secondly, it advances “disassembly definition assembly”, to plan assembly activities. The disassembly activities are summarized into spiral movement, linear motion and other types of disassembly activities, through the order of disassembly activities, the attributes of disassembly activities to do “reverse operation” to define the assembly activities. Finally, based on the MBD-based assembly information model and the “disassembly definition assembly” mode, the 3D assembly process planning system is developed to verify the feasibility and rationality of the scheme through the application of manufacturing enterprises, shorten the assembly process design cycle, and improve assembly′s efficiency and quality.