To solve the problem that the temperature rise of servo motor affects the precision of high precision coordinate boring machine, an active temperature control device for servo motor was developed. The internal temperature of the motor was read by the PLC program in real time, and compared with the room temperature, the cooling air flow was adjusted by the proportional valve controlled by program in four different modes, and the flow of each cooling outlet was monitored by sensors in redundant loop connection mode, so as to achieve the closed-loop control. The temperature rise amplitude and speed of the motor are restrained, and the temperature field around the motor is balanced rapidly under the influence of cooling air flow.