The invention relates to the technical field of vehicle control, in particular to an electro-hydraulic power steering system and a control method thereof. The electro-hydraulic power steering system comprises a steering motor, a steering oil pump, a motor controller and a current information collection module, wherein the steering oil pump is used for providing hydraulic energy for a steering gear; the current information collection module is arranged in the steering motor; the steering motor is connected with the steering oil pump through a clutch in a driving manner; the current informationcollection module is used for collecting current information of the steering motor; the motor controller judges the size relation between a current value and a current set value; if the current valueis larger than the current set value and the condition continues for a first set time, the motor controller controls the clutch to achieve engagement; if the current value is less than the current setvalue and the condition continues for a second set time, the motor controller controls the clutch to achieve disengagement; steering power of a vehicle is realized; and the problem that the service life of a motor is shortened due to great sudden changes, caused by response time difference between an existing driving motor and clutch control, of the rotation speed of the driving motor is solved.