Abstract: Rotor shaft assembly is an important process in the production of automotive micro motors, and its assembly process requires high precision and quality. The article systematically analyzes the assembly structure characteristics and process flow of the rotor shaft of a micro motor. This study focuses on introducing the principles and operating procedures of three process technologies: semi-automatic assembly, full process guided assembly, and half process guided assembly, and compares the assembly accuracy, production efficiency, and cost of different processes. Based on the results of process comparison, propose improvement strategies for axial preload optimization, automation equipment upgrading, and dynamic adjustment of process parameters, providing empirical support for a deeper understanding of automotive micro motors and improving the assembly level of rotor shafts.