Abstract: To meet the requirements for high-precision and multi-layer film preparation in vacuum coating of large-scale workpieces with complex curved surfaces, the JCPY-4.2D vacuum coating robot system was developed. Adopting a structural design of a 5-degree-of-freedom (5-DOF) Cartesian coordinate robot plus a rotary mechanism, the robot is adapted for magnetron sputtering coating under the working environment of 15℃~120℃ and 2×10⁻³ Pa working pressure, and can achieve a repeated positioning accuracy of ±1 mm and a target-substrate distance control accuracy of ±3 mm under a load of 30 kg. The solid modeling and interference check of the robot body were completed by SolidWorks; the static simulation of key components was carried out based on ANSYS; a digital twin real-time simulation system was developed by Unity3D, and multi-axis coordinated control was realized in combination with the EtherCAT bus. The results of the pre-acceptance and final acceptance experiments show that the maximum movement speed of the robot in a vacuum environment reaches 2.87 m/min (95.7% of the 3 m/min design requirement), the measured repeated positioning accuracy is 0.78 mm, and the sheet resistance uniformity of the ITO film coated on the special-shaped workpiece with dimensions of 3300 mm×1300 mm×800 mm is ±4.37%, which is better than the technical index of ±5%. This robot system solves the problem of tracking coating on complex curved surfaces, and provides a reliable technical solution for the coating processing of large-scale precision components in the aerospace, military industry and other fields.