The invention provides an oil supply device for a clutch hydraulic system. The oil supply device comprises a motor, a main cylinder and a drive mechanism, wherein the main cylinder comprises a cylinder body and a piston arranged inside the cylinder body; one end of the cylinder body, far away from the motor, is provided with an oil outlet; and the drive mechanism is connected with the piston and an output shaft of the rotor respectively and used for transforming the rotation of the output shaft of the motor to the movement of the piston along the axial direction of the cylinder body. The clutch hydraulic system can be supplied with oil by the oil supply device for the clutch hydraulic system, the oil supply capacity can be obtained by calculating the stroke of the piston through the rotation angle of the motor, and therefore the control on the oil pressure inside a clutch hydraulic cylinder is realized. Compared with the prior art, the oil supply device has the advantages of no deviation of oil supply capacity, strengthening of control on the oil pressure inside the clutch hydraulic cylinder, and reduction of probabilities of incapability for normal separation and normal jointing of a clutch. The invention also provides a control system of the oil supply device for the clutch hydraulic system as well as a hybrid electric vehicle.