Abstract: Fracture failure of locker on one automotive engine cover was occurred. By means of chemical composition analysis, metallographic examination, mechanical properties testing and so on, the fracture cause of the locker were studied. The results showed that the material of SCM435 steel was not treated by spheroidizing annealing, the hardness of material was high, and there was hydrogen embrittlement in galvanized process, resulted in locker fracture. The problem of fracture failure was solved by replacing spheroidizing annealing treatment for SCM435 steel, and improving processing technology.