Abstract: The automobile wiper arm base cracking when it was installed. The cracking reasons of the wiper arm base were analyzed by means of macro analysis, chemical composition and hardness analysis, scanning electron microscopy (SEM) analysis, metallographic examination and so on. The results show that the cold shut defect and improper assembly caused the cracking of the wiper arm base in assembly, and the cold shut defect was the main factor. The cold shut defect in the wiper arm base was caused by improper mold structure and improper control of cooling module parts.