Abstract: Fracture morphology, microstructure, micro-area composition and micro-hardness were analyzed by means of stereo microscopy, scanning electron microscopy, energy dispersive spectroscopy and micro-hardness tester.The results indicate that the fracture mode of aluminum-silicon alloy shell is brittle cracking.There are many pinhole defects in the aluminum-silicon alloy, the modification of the microstructure is insufficient, and there are many acicular phases in the microstructure, which reduces the plasticity of the casting, resulting in the shell body brittle cracking.