The invention provides a hill starting assistance system, which gathers multifaceted electrical signals, automatically controls releasing and triggering of a hill starting assistance function, and does not affect the normal driving operation; and the function is achieved simply, calibration is easy, and the cost is low. A total braking valve is connected with a first pressure switch, and then is connected into a first opening of a relay control piston of a differential relay valve in a communication mode, a parking braking air cylinder is connected with an air inlet of a two-position three-waynormally closed solenoid valve, an air outlet of the two-position three-way normally closed solenoid valve is connected with a second pressure switch, and then connected with a second opening of therelay control piston of the differential relay valve in a communication mode, an air vent of the two-position three-way normally closed solenoid valve is in communication with the atmosphere, a firstcommunication opening of a main piston of the differential relay valve is connected with a rear bridge loop air cylinder, a second communication opening of the main piston of the differential relay valve is connected with a middle rear bridge brake chamber, and TCUs are correspondingly electrically connected with the first pressure switch, the second pressure switch, the two-position three-way normally closed solenoid valve, a hill detection unit, and a function release switch through connecting lines.