Injection device is one of key parts of Squeeze Casting Machine, and scrapping phenomena is the pivotal knot of leading to injection devices malfunction and lifetime cutting of shot sleeve. The transfiguration values of shot sleeve and plunger tip in radius direction were computed out through FEM, and qualitative analysis was made on scrapping phenomena of the injection device. The results show that the clearance decreased between shot sleeve and plunger tip during injection process is the main reason leading to the scrapping.