The invention provides a transmission coaxial focusing powder feeding nozzle, which comprises a fixed mirror holder, a coupling sleeve, a nucleus nut, a thread coupling sleeve, an inner conical sleeveand an outer conical sleeve, wherein, two contact flanges which are in abutting joint are arranged outside the fixed mirror holder; two gland bushes, two refrigerating seats and a seal body are arranged inside the fixed mirror holder; four screw holes are evenly distributed in the middle of the outer wall of the seal body at intervals; the coupling sleeve comprises a transitional coupling sleeve,a front end coupling sleeve, a locking coupling sleeve and a bushing; a plurality of regulating screws are arranged on the periphery of the bushing; the transitional coupling sleeve and the fixed mirror holder are connected with each other by screw thread; the front end coupling sleeve is sheathed outside the transitional coupling sleeve; the upper end of the front end coupling sleeve is connected with the nucleus nut; a plurality of adjusting screws are evenly distributed on the periphery of the nucleus nut; one end of the thread coupling sleeve is arranged in the nucleus nut, while a regulating nut is sheathed on the other end of the thread coupling sleeve; the regulating nut and the inner conical sleeve are connected with the outer conical sleeve; a cold water tank is arranged in the inner conical sleeve; and a powder channel chamber is formed between the outer wall of the inner conical sleeve and the inner wall of the outer conical sleeve. The powder feeding nozzle can complete instant powder feeding, even powder feeding, and focus adjusting in a small range.