A conical gear convenient for adjusting axial gaps comprises a transmission shaft, a conical gear and a plurality of flat keys, wherein the conical gear is movably connected with the transmission shaft, nuts are arranged on the transmission shaft at two sides of the conical gear, and a plurality sets of key-seatings are arranged in the conical gear. Flat keyways are arranged on any nuts on positions corresponding to any set of key-seatings, and any set of key-seatings are fixedly connected with the flat keyways through the flat keys. Any nut is moveably connected with the transmission shaft and provided with a thrust gasket. The conical gear is in threaded connection with the transmission shaft, and any nut is in threaded connection with the transmission shaft. The conical gear is simple in structure and convenient for use and adjusting, high in accuracy and low in processing cost.