The invention relates to an auxiliary
downgrade controlling method for a
hybrid electric vehicle, which comprises the following steps that: (1) an auxiliary ramp controlling
system is arranged and comprises a finished vehicle controller, a motor, a
motor controller, an engine, an engine controller, a hydraulic braking device and a hydraulic braking device controller; (2) the finished vehicle controller acquires the position of an accelerator pedal, the position of a braking pedal, the position of a gear shift and the information of vehicle speed in real time to judge whether the vehicle enters a ramp assisting program; and (3) the finished vehicle controller calculates the corresponding
brake torque through the variable quantity of the vehicle speed; and according to the battery SOC, the
brake moment of the motor, the vehicle speed, the state of a
clutch and the gear shift of a speeder, the reverse drawing of the motor and the engine and the
brake moment of the hydraulic
braking system are uniformly and dynamically coordinated to keep the vehicle speed in
relative stability. The method lightens the fatigue degree of the operation of a driver and also improves the
driving safety and the fuel economy of the vehicle.