Mg-alloys have broad application prospects in fields such as aerospace and automotive manufacturing due to their lightweight and high-strength characteristics. However, their poor corrosion resistance limits their widespread application. This study aims to systematically investigate the effect of different Al contents on the microstructure and corrosion behavior of Mg-xAl-Zn (x = 3, 6, 8) alloys. Alloys with varying Al contents were prepared by extrusion, and their microstructures and phase compositions were analyzed using Scanning Electron Microscope (SEM) and X-ray Diffractometer(XRD). The corrosion behavior of the alloys in 3.5%NaCl solution was evaluated through electrochemical tests, hydrogen evolution measurements, and mass loss analysis. Increasing the Al content facilitates the precipitation of the β-Al₁₂Mg₁₇ phase, and the morphology and distribution of this intermetallic compound significantly affect the corrosion properties of the alloys. During corrosion, the β-Al₁₂Mg₁₇ phase acts as a cathodic site, thereby accelerating the corrosion of the Mg-matrix. In general, a larger cathode-to-anode area ratio results in a higher galvanic corrosion rate. A compact surface film formed during the corrosion process of an alloy can provide certain degree of protective effect, thereby improving its corrosion resistance. It follows that as the Al content increases, the corrosion resistance of the alloy first improves and then decreases, among others, the AZ61 (Mg-6Al-Zn) alloy exhibits the best corrosion resistance.