Hydraulic motor speed regulating system was presented to achieve the functionality of speed control by combining a fixed high-speed on/off valve, a cartridge valve, a one way valve and an accumulator etc. Its main structure mechanism and application characteristics were introduced. The corresponding math models of main components were set up. The related theory analyses were also carried out. The speed ratio and efficiency simulation analyses of the speed regulating system were done by AMESim. The results show that the hydraulic transmission system has high efficiency and a good dynamic response.