Superamphiphobic surface films were successfully prepared on AZ31B Mg-alloy via etching with HNO₃ solution and afterwards modifying with PFDTES (1H, 1H, 2H,2H-perfluorodecyltriethoxysilane). The superamphiphobic surface film were characterized by means of scanning electron microscope (SEM), X-ray diffractometry (XRD), X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectrometer (XPS). The static contact angle (CA) was measured by optical contact angle meter to estimate their wettability, The electrochemical performance was evaluated in 3.5%NaCl aqueous solution by electrochemical work-station to estimate their corrosion resistance. Results show that the non-uniform distribution of chemical composition of the Mg-alloy leads to different dissolution rates and degrees of the alloy surface during the etching process, resulting in different morphology on surface. The special microstructure formed on the etched alloy surface, combined with the modification of low surface energy materials (PFDTES), enables the formation of a film with excellent liquid repellency on Mg-alloy. The contact angles (CAs) of water and ethylene glycol on the modified Mg-alloy surface were 159.3° and 155.2° respectively. In contrast to the bare Mg-alloy, the free corrosion potential of the superamphiphobic film covered Mg-alloy shifted positively by 297 mV, and the corrosion current density decreases by more than 3 orders of magnitude, the charge transfer resistance increases by more than 2 orders of magnitude, in other word, the anti-corrosion performance of the AZ31B Mg-alloy was well improved by the surface modification. Even after soaking in 3.5%NaCl solution for 72 h, the Mg-alloy with superamphiphobic film still maintains good corrosion resistance.