Automatic shearing system and method for vehicle safety belts

The invention discloses an automatic shearing system for vehicle safety belts, which is used for automatically shearing the safety belts when vehicles are collided violently. The automatic shearing system for the vehicle safety belts comprises a collision sensor, an information processor and a safety belt shearing device, wherein the collision sensor is used for sensing a collision strength signal of the vehicle and informing the information processor; the information processor is used for converting the collision strength signal into a collision decision value and comparing the collision decision value with a collision critical value; and when the collision decision value is more than or equal to the collision critical value, the safety belt shearing device is controlled by the information processor to cut off the safety belt after the vehicle collision. The invention further provides an automatic shearing method for the vehicle safety belts. Through the automatic shearing system and the method for the vehicle safety belts, motorists and passengers can be prevented from being trapped in the vehicles due to safety belt failure.