Abstract: Aiming at the problem of inaccurate workpiece position in the assembly process of infrared sensor, an automatic assembly system of infrared sensor based on visual recognition and positioning technology is designed. The mechanical structure of the system is composed of industrial robot, feeding unit, conveying unit, visual detection unit, quick-change tool unit, the seventh axis of industrial robot, etc. The position and angle of the sensor end cover are recognized by the vision system, and the result is converted to the robot world to make the workpiece can be grasped accurately. A PLC control system based on Ethernet communication is built to complete the discharging, conveying, grabbing and automatic assembly control of infrared sensor parts. The experiment shows that the designed system has high degree of automation, reliable operation and high promotion application value.