The work aims to improve corrosion resistance of Mg-Li alloy by depositing pure Al film on a sample by means of PVD magnetron sputtering technology. The electrochemical behavior of Mg-Li alloy in deionized water and 3.5% NaCl solution was studied by virtue of dynamic polarization curve and AC impedance spectrum. The alloy composition was determined and microstructure was analyzed by virtue of inductively coupled plasma emission spectrometer (inductively coupled plasma-AES) and fluorescence metallographic microscope. The morphology and compositionof pure Al film on Mg-Li alloy were analyzed by scanning electron microscope (SEM) and energy disperse spectroscopy. The electrochemical behavior of the sample with pure Al film was also tested on electrochemical workstation. For uncoated Mg-Li alloy, the corrosion current density was two orders of magnitude higher than that in deionized water when tested in 3.5% NaCl solution, the corrosion potential was more negative. According to alternating-current impedance results, the impedance modulus value obtained in 3.5% NaCl solution was about one order of magnitude lower than that in deionized water. Compared with uncoated alloy, resistance of Mg-Li alloy to Cl? corrosion was weaker. A 4 μm dense pure Al film was obtained by virtue of magnetron sputtering technology. After being aluminized, corrosion current density of the Mg-Li alloy reduced by nearly one order of magnitude, the corrosion potential moved positively and corrosion resistance increased. Dense pure Al film is susceptible to passivation in 3.5% NaCl solution, hindering the diffusion of Cl? and further improving the erosion resistance of Mg-Li alloy to Cl?.