The utility model discloses a have semi -axis of sun gear function concurrently. Including one semi -axis main part, semi -axis main part one end outer loop surface machining has the spline, and other end outer loop surface machining has the teeth of a cogwheel. The outer cover of spline be equipped with with its self -contained complete differential side gear to be connected with the differential side gear meshing, the teeth of a cogwheel and with install on the planetary gear racks planet wheel meshing and be connected, the terminal surface of the teeth of a cogwheel is near the interior side surface of planetary gear racks. Adopt the utility model discloses can make the semi -axis have the sun gear function concurrently, close semi -axis and sun gear into one whole, simplify the processing technology process, save the material, and the supplementary spare part of will not when producing traditional semi -axis with the sun gear assembly, simplify the installation and examined and repaired the step, be applicable to various engineering mechanical drive bridges.