In the past years, Models QZ100K and QZ100B tripod DTH drills were used in the construction of most works such as open-pit side, building and quarrying etc. However, the problems on the reduction gearbox for this type of drills lie in large volume, heavy weight, small transmission torque and low efficiency etc. In order to solve these problems, the reduction gearbox, which matches Model QZ100KJS drill, was developed by The Machinery Factory, Changsha Institute of Mining Research. This reduction gearbox is driven with the two-stage planet gears, and features compact structure, small volume, low weight and great transmission torque etc. After putting into operation, its good technical performance has been shown.