Abstract: This paper investigated the galvanic corrosion behavior and laws of AZ91D, AM50 and AM60 cast magnesium alloys coupled with four materials of Q235 carbon steel, H62 brass, 316L stainless steel and LY12 aluminum alloy under atmospheric exposure in Qingdao and Wuhan of China for three, six, fifteen, twenty, twenty-seven months. The results show that the magnesium alloys act as the anode and their corrosion rates obviously increase when coupled with the four materials used in this test. The atmospheric galvanic effects of the magnesium alloys coupled with Q235 carbon steel and 316L stainless steel are larger than those of others, while that of the magnesium alloy/LY12 aluminum alloy couple is the smallest. The atmospheric galvanic effect in Qingdao is obviously higher than in Wuhan. Among the experimental magnesium alloys the maximum atmospheric galvanic effect was found in the test of AZ91D, while AM50 the minimum.