The liquid oxidation behavior of Mg-Ca base alloys containing Be has been presented in this paper. The ignition temperature test and microbalance measurement indicated that the oxide film formed at elevated temperature was protective, resulting in the improved oxidation resistance and ignition-proof properties. A Ca-rich zone was found at the very near surface of oxide layer. With Be addition the oxide layer became dense and compact, which was impermeable for the rapid diffusion of oxygen and magnesium through the oxide layer. It was concluded that the formation of BeO in the oxide layer suppressed the continuous growth of the oxide layer.