Scientific drilling is called mans “Underground Telescope”. Its an important way solve a series of energy, resources, environmental problems during the development process. Topdrive is designed to meet the demand of petroleum drill. Existing topdrive can’t afford enough speed for multipurpose deep exploration. It’s need to design rotary drill for deep stratum to meet demand. The general planning of the hydraulic system of the hydraulic top drive system was determined. Its working principle was discussed and its hydraulic schematic diagram was drawn.