Abstract: In the hot forging of H13 steel, hole defects often appear in the roughcast of the die, and samples are taken at the defects, and the causes of the hole defects are examined and analyzed. The results show that the internal mold blank hole defects is due to the presence of carbide eliquation, inclusions and other defects in steel metallurgy, steel in upsetting, from defects form stress concentration appears in the impact load stress cracks, with the increase of continue to impact load and deformation, the crack expanded form holes; main causes of carbide eliquation, osteoporosis is caused by the high temperature casting steel, through the optimization of casting process of steel, so that the mold blank forging hole defects basically elimination.