Abstract: In order to prevent water hazard effectively and meet the needs of dilling for water detection and drainage in coal mine, special ZDY3500 T drilling rig wi th high-speed and long stroke, suitable for drilling hole of 300 m deep is developed. The waterproof design, feeding device, substantially variable amplitude mechanism, slip assembly, large opening holder, power pumps and safety device of the wellhead, are introduced in the paper. Test shows that the ZDY3500 T rig can meet the need s of drilling drainage borehole in majority of coal mines due to its advanced technique solution and provides reliable equipment to reduce water hazard in coal mines.