The Corrosion behaviour of Mg-7.3Al alloy in buffered chloride solutions was investigated in the paper. The corrosion resistances of Mg-7.3Al alloy were evaluated in different borate capacity and pH by immersion test and polarization curves. The influences of immersion time, pH and buffer borate capacity were analyzed. The results revealed that the corrosion rate of Mg-7.3Al alloy depends on the pH of corrosive solution and has no relationship with buffer capacity. In the pH 6.5 and 2g / L buffer solution, the morphologies of Mg-7.3Al alloy consist of porous pits and protuberant second phases. There are seriously corroded area and macro-uncorroded area or protuberant second phases on the sample surface. The corossion potentials of the mg alloy is kept the same value in the pH 9 solution, regardless of borate capacity is 1g/Lor 2g/L, which are higher than that in the neutural chloride solution or acid solution (pH=6.5). Borate may play an inhibition role for mg alloy by the quick corrosion test of polarisation curves.