The invention provides a pressure casting split type punch injection device which comprises a punch, a charging barrel, an injection cylinder, a base and a push rod. According to the injection device, the punch is a split type punch formed by sleeving a plurality of sub-punches with different or identical radial size or section shape; and the assembling relationship is that the plurality of sub-punches with different or identical radial size or section shape are sequentially arranged in a sleeving manner from interior to exterior according to increasing radial sizes and are in axis coincidence with one another, and every two adjacent sub-punches are in clearance fit. According to the invention, a split type structure of the punch is realized, the multiple sub-punches can independently move relative to one another, and different pressures can be applied to different parts of the casting, so that the punch can directly act on the casting in shape. In the mold filling process, molten metal can be pushed into the cavity according to a set sequence according to demands of the casting, which is very favorable for forming composite materials. Therefore, the casting quality can be effectively improved.