The utility model discloses an auxiliary system for emergency braking of a compact car. The auxiliary system for emergency braking of the compact car comprises parallel plates which are hinged to a connecting plate of a car chassis, wherein a braking vane is hinged to the bottoms of the parallel plates, a hydraulic cylinder is arranged between the car chassis and one of the parallel plates, and the hydraulic cylinder is connected with a hydraulic cylinder control system arranged in a car cab. When the auxiliary system for emergency braking of the compact car is used, the auxiliary system for emergency braking of the compact car is installed on the at the portion, close to the rear portion, of the center of the bottom of the car chassis, the braking vane is contracted by the auxiliary system to the position below the car chassis through the hydraulic cylinder in the normal traveling process of the compact car, and passing capacity of the compact car is not affected; when emergency braking needs to be carried out in an emergency, the braking vane is released by the auxiliary system through the hydraulic cylinder, the braking vane makes contact with the ground, friction is increased to carry out auxiliary braking, and the braking distance can be effectively shortened.