An injection head structure of a die casting machine contains: a base including a first inlet and a plunger rod. The base also includes a through hole, a head block having an outlet, and a neck having a guiding hole. The plunger rod is mounted in the through hole and includes a receiving groove, a second inlet, and a feeding orifice. The through hole of the base has an inner conical face formed around an inner wall thereof; the plunger rod includes an outer conical face arranged around an inner wall thereof, such that when the plunger rod is inserted into the through hole of the base, the inner conical face of the base contacts with the outer conical face of the plunger rod so that the base engages with the plunger rod.