The invention relates to a hydraulic system of a flexible rod vibration test bench. The system comprises a power source hydraulic system, a stretch hydraulic system, two push hydraulic systems and a twist hydraulic system, wherein the power source hydraulic system is simultaneously connected with the stretch hydraulic system, the two push hydraulic systems and the twist hydraulic system; the stretch hydraulic system is connected with a stretch load device of the test bench; one of the push hydraulic systems is connected with a front-back swing load device of the test bench, and the other push hydraulic system is connected with a left-right swing load device of the test bench; the twist hydraulic system is connected with a twist load device of the test bench. The stretch hydraulic system, the two push hydraulic systems and the twist hydraulic system are driven respectively through the power source hydraulic system to work independently, push, pull and twist functions of a test object are realized, and higher control precision is achieved through electro-hydraulic combined control. Meanwhile overload can be very easily prevented, and the safety coefficient is high.