Based on Ansys software, the influences of shape, size, position and pitch of holes on AZ91D Mg alloy die casting stress distribution were studied. The results show that the influences of shape of hole on stress distribution lie on the minimum included angle formed by two lines, one line is x axis, the other is the tie line of sharp corner apex and center of hole. The stress concentration increases with the increases of the minimum inclination and the size of hole. The influence effect of the open hole is greater than the inner hole. The influence is very faint when the pitch of holes is beyond a critical value, and the stress concentration increases quickly with the decrease of the pitch of holes. Lastly, the hole distribution and the strength of AZ91D Mg alloy for engine head mantle die casting are actually measured. It is shown that the results of theoretical analysis are in consonance with the experiments.