The oxidation behavior of a Pd40Ni40P20 (in at. %) bulk-metallic glass (BMG) was studied over the temperature range of 350~450℃ in dry air. The oxidation kinetics of the BMG alloy generally followed the parabolic rate law, with its oxidation rate increasing with temperature. Based on transmission electron microscopy (TEM) analyses, an NiO layer formed on the BMG surface after the oxidation, and a Pd-rich layer formed beneath the scales. After a short-term oxidation at 390℃ for 10 min, the amorphous substrate was transformed into two crystalline phases of Pd3P and Ni3P, indicating a phase transformation of the substrate at the initial-stage oxidation.