Abstract: The corrosion behaviors of AM-SC1, AZ91D and NZK magnesium alloys in CALTEX coolant with KF addition were studied through weight loss experiment, electrochemical test and XPS analysis. Results show that increasing the KF addition in the CALTEX coolant, the corrosion rates of three alloys decreased. The inhibitive effect of KF on corrosion of AM-SC1 and NZK alloys was significant. The reason KF inhabited corrosion of alloys was due to the formation of a layer of low solubility magnesium fluoride film, because of the reaction between fluorinion and magnesium on the surface of alloys, and prevented further corrosion attack to the alloys.