Motor vehicle auxiliary brake device

The utility model relates to a motor vehicle auxiliary brake device, which comprises a guide rail with an opening at the bottom, wherein the guide rail is internally provided with a fixed block ,a reset spring and a slide block, the fixed block is fixedly connected into the guide rail, the slide block is in sliding fit into the guide rail and is fixedly connected with a push rod and a limiting mechanism, the guide rail is provided with a locating hole which is matched with the limiting mechanism, the lower parts of the fixed block and the slide block extend from the opening at the bottom of the guide rail, a bracket is hinged between the lower part of the fixed block and the lower part of the slide block and comprises a first connecting rod, a second connecting rod and a third connecting rod which are hinged sequentially, and the bottom of the second connecting rod is provided with a friction plate. When the motor vehicle is emergently braked, the auxiliary brake device provided by the utility model can enabl