Arc-glow plasma depositing technique is a new surface coating method. With the help of vacuum arc discharge, a cold cathode arc source continually emits ion beams of coating elements with high currency density and high ionizing ratio. Upon the ion bombard and diffusion work on, the surfaces of the parts form deposited layers, diffusion layers. In this study, a commercial magnesium alloy AZ91 was coated with Ti film layer. The corrosion behaviors of the coated samples have been studied by methods of measuring anodic polarization curves and salt spray test. Section and surface morphology of Ti film have been surveyed through scanning electronic microscopy (SEM), the composition analyzed by electron diffraction spectrum (EDS) and glow discharge spectrum (GDS). The results indicated that the coating of Ti effectively improved the anti-corrosion performance of AZ91.