The invention provides a medical bone nail. The medical bone nail comprises an octagonal connecting rod, an octagonal screw cap, a round connecting rod, a round screw cap, a first round rod, a first through hole, a spiral connecting piece and a second round rod, wherein the octagonal screw cap is arranged on the octagonal connecting rod in a sliding and sleeving way; the round connecting rod is fixedly arranged at the top of the octagonal connecting rod; the round screw cap is arranged on the round connecting rod in a threaded sleeving way; the first round rod is fixedly arranged on the octagonal connecting rod; the first through hole is formed at the bottom end of the first round rod; the spiral connecting piece is arranged in the first through hole in a sliding way; the bottom end of thespiral connecting piece extends out of the first through hole; and the second round rod is arranged in the first through hole in a sliding way. The medical bone nail provided by the invention has theadvantages of convenience in use, capability of singly changing the connecting piece on the bone nail according to requirements, capability of saving resources and simplicity and convenience in operation.