Computer Aided Assembly Process Planning and Simulation in 3D environment depends mainly on the manner of human-computer interaction currently in the airplane manufacturing industry, and in fact it’s just a recorder for recording the designers’ assembly intention. It’s short of supports for a designer to execute the 3D assembly process planning and simulation, for lacking a strict process flow definition and a pilot method. In this respect, we propose a decomposition modeling method of 3D assembly process planning and simulation for airplane subassembly named Assembly Process Micro-Planning and Simulation (APMPS), which defines a standardization flow and a data-information modeling method. By using this method, the assembly process can be designed and validated form assembly-design-intention to assembly-process-planning to assembly-process-simulation with the five process levels’ definition (AJATAOAAAM). This method is validated by a central-wing’s assembly process design in an airplane manufactory. The result shows that the APMPSS is in accordance with the Concurrent Engineering’s requirements, and it can be carried out fast in 3D environment.