The present invention discloses an octave-key transfer-bar protection device, which is installed on a saxophone to protect an octave-key transfer-bar on the saxophone, and which comprises a structure body, and a collision-protection bar arranged on the structure body and encircling an accommodation space. The structure body is fixed to the external surface of the saxophone. The octave-key transfer-bar is arranged inside the accommodation space and encircled by the collision-protection bar. The collision-protection bar can protect the octave-key transfer-bar from being deformed by collision. Thus, the performer can correctly lower or raise the gamut via the octave-key transfer-bar.