Abstract: This automatic positioning system is designed for the crane which is in common use. The crane hall is cut into several parts, the position is detected by the photoelectric switches, and the PLC and inverter are used for the control devices. The automatic positioning control of the crane is completed by means of the timing movement. The positioning error is less than 2.1cm, the swing range when lifting object is less than 5.7cm, and the average speed of the crane is more than 90% of the rated speed. This paper gives further description in the positioning control, direction control, speed control and the identification of the starting point. Finally it gives an analysis of the automatic positioning performance.