The invention relates to a medical instrument, in particular to a bone nail countersink drill for the orthopedics department. The bone nail countersink drill comprises a bearing installation base anda bearing. The bearing is fixedly connected into the bearing installation base. A rotating shaft is fixedly connected with the inner ring of the bearing and penetrates through the bearing installationbase. A bone nail countersink drill stem is fixedly connected with the outer end of the rotating shaft. A gear is fixedly connected with the inner end of the rotating shaft. Two rotating rod fixing pieces are perpendicularly and fixedly connected with the upper end of the bearing installation base. A rotating rod is movably connected between the two rotating rod fixing pieces through a movable shaft. A rectangular rack fixing hole runs through the middle of the rotating rod. A rack is movably connected into the rectangular rack fixing hole through a pin shaft. The bone nail countersink drillis scientific and reasonable in structure, simple and convenient to operate and control, high in drilling efficiency, good in drilling quality, capable of shortening the time of orthopedic surgery andimproving the technological level of the orthopedic surgery and suitable for use and popularization.