Considering the practical applications of Mg alloys, which are mainly in automobiles and housing utensils, Mg alloys are frequently used in atmospheric conditions. In this research, we systematically exposed several Mg alloys (including AM20, AM50, and AZ91) to different atmospheric environments with different concentrations of environmental variable. A detailed investigation was performed to understand the role of NaCl, CO2, SO2 and temperature using carefully controlled laboratory experiments. The study elucidates the interplay between the alloys’ microstructural constituents (α, β, η and casting pores) and the changes in the atmosphere, and, thus, provides a mechanistic understanding of the atmospheric corrosion behavior of Mg alloys. It is expected that the findings presented of this study can contribute interpreting the corrosion behavior of Mg alloys in different climates.