The stress corrosion cracking and hydrogen embrittlement of the Al-xMg-3.1Zn aluminum alloys were studied by slow strain rate tensile tests and dynamic electrolytic hydrogen charging experiments, respectively. The effect of Mg on the stress corrosion cracking behaviors was indicated combining with transmission electron microscopy and fracture analysis. The results showed that the stress corrosion cracking was happened in the studied alloys, and the corrosion susceptibility decreased with a decrease of Mg content due to the decrease of the grain boundary precipitates continuity. This was result from the decrease in the anodic dissolution of grain boundary precipitates and hydrogen embrittlement behaviors with a decrease of Mg content.