The invention aims at providing a hydraulic control system for a fatigue test machine for a bearing bush of a cam-driven proportional overflow valve. The hydraulic control system for the fatigue testmachine for the bearing bush of the cam-driven proportional overflow valve comprises a hydraulic oil cylinder, an eccentric link mechanism, a drive motor, an oil tank, a hydraulic oil pump of an upperoil cylinder and a hydraulic oil pump of a lower oil cylinder, wherein the drive motor is connected with the eccentric link mechanism and drives the eccentric link mechanism; the hydraulic oil cylinder is divided into the upper oil cylinder and the lower oil cylinder through a piston; a piston link is connected with the eccentric link mechanism; the hydraulic oil pump of the upper oil cylinder isconnected with a hydraulic oil pump motor of the upper oil cylinder; an oil inlet port of the hydraulic oil pump of the upper oil cylinder is connected with the oil tank; an oil outlet port of the hydraulic oil pump of the upper oil cylinder communicates with the upper oil cylinder; the hydraulic oil pump of the lower oil cylinder is connected with a hydraulic oil pump motor of the lower oil cylinder; an oil inlet port of the hydraulic oil pump of the lower oil cylinder is connected with the oil tank; an oil outlet port of the hydraulic oil pump of the lower oil cylinder communicates with theupper oil cylinder; and the upper oil cylinder is connected with the oil tank. The hydraulic control system for the fatigue test machine for the bearing bush of the cam-driven proportional overflow valve is capable of ensuring that an in-cylinder pressure of the control system is approximate to an in-cylinder combustion pressure of a low-speed machine, so that the capacity of reflecting the realworking condition of a testbed is greatly improved.