Abstract: In order to solve the problem of difficult maintenance of foreign control systems, the paper took the domestic Huazhong HNC-818DiM as the research object and implements the upgraded of VMC850 machining centers, focused on solving the key technologies of control line design, PLC program development and electromechanical intermodulation. Through actual cutting verification, the upgraded machining center has improved its positioning accuracy and repeatability accuracy, fully meeting the requirements of high-speed and high-precision machining. The performance and processing accuracy after the transformation meet the relevant standard requirements. This provides a basis for the digital upgrading and transformation of machine tools with different structures.