The invention discloses a hydraulic system for testing a hydraulic torque converter; the hydraulic system comprises a main controller, a detection module connected with the input end of the main controller, a hydraulic torque converter and an oil tank; the detection module comprises a temperature sensor, a flow detector and a pressure sensor; the input end of the main controller is connected with a manual electromagnetic valve and the output end thereof is connected with a pressure gauge and a hydraulic pump by means of an A/D conversion module; the output end of the main controller is connected with a heater, a cooler and a proportional regulating valve; the oil discharging pipeline of the oil tank is connected with one end of the hydraulic torque converter by means of an oil suction filter, the hydraulic pump and the proportional regulating valve; the other end of the hydraulic torque converter is connected with the oil return pipeline of the oil tank. The hydraulic system is capable of cooling the hydraulic torque converter, protecting the mechanical property of the hydraulic torque converter and simultaneously regulating the pressure by means of a manual regulating valve and an automatic regulating valve, is convenient in operation, rational in design, convenient in usage and operation, high in control reliability, high in work stability, good in usage effect and convenient in promotion.