The assembly of some parts during the assembly process of an automobile gearbox involves the process of selecting and adjusting gaskets. Whether the gasket size is appropriate will directly affect the overall assembly quality of the gearbox. In order to meet the production requirements of the new model gearbox and meanwhile improve the precise ability of the production system, it is necessary to transform the traditional manufacturing mode dominated by manual experience into a lightweight, intelligent new manufacturing model. In order to improve the digitization of the production site and the ability to manage the measurement tasks, the research has designed and implemented a new measurement system for gearbox assembly. The system is based on MQ250 gearbox assembly line. The research begins with the whole structure, and introduces the measurement module of the software system. First, based on the principle of relative measurement, a measurement module was designed, and the optimization problem of the measurement module was analyzed. Finally, the optimization of the measurement module was achieved by the least square method. The measurement system adapts to the assembly requirements of MQ250 gearbox components, and improves the assembly quality under the condition of ensuring assembly efficiency, and greatly improves the digital level of the assembly line while ensuring the assembly efficiency.