Abstract: The fracture of locating columns of gear housings made from aluminum alloy happened before and during assembly period. Means such as chemical composition analysis, fracture macrographic examination, scanning electronic microscope and energy spectrum analysis, metallographic examination were used to comprehensively analyze fracture reasons of locating columns. The results show that:the improper casting process of gear housings resulted in the casting defects in casting pieces, such as amounts of gas porosity, shrink porosity and cold shots, which was the main reason for the brittle fracture of locating columns of this batch of gear housings. Finally, the improved measures were brought forward for casting process of gear housings.