Abstract: A servo pressure control system for precision spot welding was designed to solve the high mechanical impact, high pressure fluctuation, non-control of pressure and electrode position during spot welding process with pneumatic welding gun. The system adopted the compression mode of servo pressure and spring follow-up, and used high-precision pressure sensor to check the electrode pressure. Based on the DSP controller, the precise control of welding pressure and electrode displacement was realized. With the method of staged control, the system realized the electrode rapidly pressing down and contacting with the workpiece in a soft way, and it was also beneficial to optimize welding pressure speed, which has wider process adaptability. The experimental results show that the system has high pressure speed, smooth transition of pressure curve, and obvious influence of welding starting pressure on welding quality.