The invention discloses a gear operating device for a drilling machine. A loading-unloading tool comprises a rod body and a working head fixed to one end of the rod body, wherein the working head is clamped to a groove on an external thread protector, when the working head is clamped to the groove on the external thread protector, and the axis of the rod body is perpendicular to a rotating shaft of the external thread protector. The gear operating device is simple in structure, is convenient to operate, solves the problem that the working efficiency is not high when the external thread protector of an external thread joint of a petroleum drilling tool is loaded and unloaded, enables the working efficiency of operation of the petroleum drilling tool to be greatly improved, and enables the working intensity to be reduced.