Abstract: A steel bracket used in a vehicle fractured during the durability road test. The failure part and the qualified part in the durability test were compared, and the fracture reasons were analyzed by chemical composition analysis, static tensile test, metallographic examination and fracture analysis. The results show that:the carbon content in the material of the failure bracket was extra low, and grain-boundary strength of the material was weak; the large pressing deformation happened to the fracture position of the bracket, which led to the large stress; secondary working embrittlement was the root reason of the intergranular fracture failure of the bracket.