Abstract: Cracking failure occurred in A380 aluminum alloy mounting bracket of a gearbox during bolt installation in the whole vehicle production line.The causes of cracking failure of mounting bracket were analyzed by macro examination,chemical composition analysis,metallographic examination,fracture analysis,hardness and density test.The simulation was carried out under different process conditions,and the process condition causing cracking were obtained.The results show that during the casting process,a large number of aluminum oxides formed in the mounting bracket due to the mixing of demoulding agent and the aluminum oxides,which resulted in the decrease of material strength,was the main cause of cracking of the mounting bracket.The oxide was a casting defect formed by the reaction of a large number of demoulding agents with liquid aluminum in rapid die casting under cold die condition.