Porous drilling machine considers that the load of the machine is larger and the speed is lower when it works. The load is smaller and the speed is higher in fast forward and fast backward. In order to save energy and reduce heating, dual pump or variable pump should be used in the pump source system. Pressure-limited variable displacement pump with pressure feedback is adopted. In the hydraulic system of small and medium-sized special machine tools, throttle valves or speed regulating valves are usually used to control the feed speed. According to the characteristics of low speed performance and speed load characteristics of special milling machine tools, the solvent throttling speed regulation composed of pressure limiting variable pump and speed regulating valve is adopted. The speed regulating circuit has the characteristics of high efficiency, fewer heat and good speed rigidity, and the speed regulating valve is installed on the oil return circuit, which can bear the cutting force of load.