Abstract: A grease gun connecting nozzle comprises an injector pipe. A support sleeve inserts inside the injector pipe. A front end of the injector pipe is locked to the structure element to be greased via a connecting element. Four movable leaves are mounted around the outer peripheral sidewall of the support sleeve. A pipe plunger made of plastics material inserts inside the support sleeve to prevent its deformation. The pipe plunger comprises a front pipe and a rear pipe with an outer radius larger than that of the front pipe. The rear pipe inserts inside the injector pipe. The front end of the pipe plunger is inwardly recessed in the shape of a bell that engages with a conical head of the connecting element. The leaves tighten a neck at a rear portion of the connecting element. Thereby, grease leakage is effectively prevented, and a rapid assembly can be achieved.