The invention discloses a hydraulic flow distributing system for distributing the pressure proportion randomly. The hydraulic flow distributing system comprises an oil tank, a split-flow valve, a metering pump, a motor and a pressure regulating unit. The oil tank, the input end of the split-flow valve and the motor are connected with the metering pump, and a coupler is connected between the motorand the metering pump. The two output ends of the split-flow valve are connected with a pilot type overflow valve and a reversing valve correspondingly. The pressure regulating unit comprises a rack,a lead screw and a pilot type overflow valve. The two pilot type overflow valves are symmetrically arranged on the two sides of the rack, and the two ends of the lead screw are connected with the pilot type overflow valve correspondingly. The lead screw comprises a screw rod and a nut spirally connected to the screw rod. According to the hydraulic flow distributing system, the ball screw is adopted as an actuating element, the pretightening force of springs of the two pilot type overflow valves is controlled by rotating the nut on the ball screw, then the pressure of the overflow valve is regulated to control the pressure of two branches, and finally distribution of any pressure proportion is achieved. The hydraulic flow distributing system is wide in application range and low in cost.