The invention discloses a belt pulley sound-light alarm alignment instrument comprising a small belt pulley, a large belt pulley and a driving belt. The driving belt winds the two belt pulleys in an enclosed way. One of the end surfaces of the small belt pulley is provided with a signal emitter, and the end surface of the same side of the large belt pulley is provided with a signal receiver. The signal emitter is a fan-shaped laser emitter which can emit fan-shaped light beams. The signal receiver is a laser receiver. The laser receiver is installed at the circumferential edge position of the end surface of the large belt pulley and positioned in the emission range of the fan-shaped light beams. The fan-shaped laser emitter and the laser receiver are respectively fixed on the small belt pulley and the large belt pulley via respective magnetic fixing frames. Four-point and one-line adjustment of the belt can be rapidly realized so that wearing of the belt and the belt pulleys can be reduced, the belt driving application field is relatively wide, reduction of belt loss is significant and onsite worker adjustment is easy and rapid.