The invention discloses a device for completing steel coil width centering on walking beam. The device comprises a large steel coil, a small steel coil, a width centering trolley, a fixed saddle, a cantilever support, a position sensor, an ultrasonic sensor and a temperature sensor, wherein the small steel coil is arranged at the bottom of the inner side of the large steel coil, the width centering trolley is arranged at the bottom of the large steel coil and the bottom of the small steel coil, the walking beam is fixedly arranged at the bottom of a sliding rail, the cantilever support is arranged at the front end of the fixed saddle, an ultrasonic sensor is arranged at the inner side end of the top of the cantilever support, the temperature sensor is arranged at the front end of the top of the cantilever support, a rotating shaft is arranged in the middle of the bottom of the cantilever support, an oil cylinder is connected to the front end of the rotating shaft, and the position sensor is arranged at the front end of the cantilever support. Width centering of the steel coil at an inlet is achieved according to a gravity center position of the steel coil, coil upending accidents are avoided, the automatic production efficiency is improved, the effect of personnel simplification is achieved, full-automatic operation is achieved, safety and reliability are achieved, measurement is accurate, and maintenance is easy.