Provided is a motor vehicle safety device. The device is installed on a guide rail in a vehicle through a seat of a driver, air cylinders are symmetrically arranged on the front and rear sides of the seat, at usual time, compressed air is introduced into the two air cylinders, and by means of a corresponding air path system, the two air cylinders are maintained in a balanced state; a travel switch is arranged on the rear portion of a bumper, and when the bumper receives an impact, the travel switch is switched on and make the air cylinders in the balanced state immediately push and pull the seat by controlling an electromagnetic valve in the air path system, so that the seat can bounce at a high speed along the guide rail inside the vehicle to avoid the coming impact.