Abstract: To study the working principle of machine tool hydraulic system and improve the installation process of hydraulic components is an effective way for machine tool producers and users to improve the overall performance of machine tool stability from the assembly details. This paper takes the hydraulic system of a well-known brand CNC lathe in China as the research object, analyzes the composition of the hydraulic system and the working principle of the representative control loop, and makes detailed normative technical requirements for the general assembly process of hydraulic components. Through the practice of machine tool production and maintenance, this technical specification can provide a certain reference for improvement of the machine tool assembly quality and comprehensive performance stability, and for the machine tool technical practitioners to master the basic knowledge of machine tool hydraulic system; at the same time, it has important guiding significance for the correct installation, debugging, use, maintenance and repair of machine tools.