Abstract: The operation of fission crawler drill rig for gas extraction in coal mine is not convenient as walking in underground coal mine and shifting in the drilling pad, because the hydraulic system is needed to be connected by tube. In order to improve convenience of the crawler walk, the hydraulic system of ZDY6500LF fission crawler drill rig is designed, and the components and principle of hydraulic system are analyzed. The new hydraulic system has the independent walking characteristics of crawler vehicle which do not need hose connection. The tubes are connected for drilling after two crawler vehicle components arrive at the drilling pad and the position is adjusted. The hydraulic system achieves the divided hydraulic transmission and independent control of the crawler walking. The testing experiment verifies the reliability of hydraulic system, and shows that the hydraulic system has very strong application value.