The span of the special crane for electrolysis is 31500 mm, the installation distance of the laser rangefinder is 30255 mm, the running speed of the crane is 0~160 m/min, the running speed of the trolley is 0~45 m/min, and the maximum acceleration and deceleration of the crane is 0.3 M / s'. Two laser rangefinders are used to measure the crane position, with a range of 300 m. the actual range is 200 m, with a measurement error of 2.5 mm and a repetition error of +1 mm. Use a coding ruler to measure the position of the trolley, and the measurement accuracy is 0.4 mm. The crane is driven by two half - one quarter corner converters. PLC control is adopted, and the data of PLC, laser rangefinder and encoder are interconnected through PROFIBUS communication protocol. Four horizontal wheels are set on one side of the crane to limit excessive synchronization error. At the same time, this method can also enlarge the horizontal wheel clearance that limits the crane synchronization deviation to 40d1/d2, where D1 is the horizontal wheel spacing and D2 is the crane gauge. After actual detection, the automatic positioning accuracy of the traveling crane and trolley is < +5mm, and the error value between the reading of the laser rangefinder and the set target value is < +1mm after the automatic positioning is stopped.