In this paper the galvanic corrosion behavior laws of AM50 magnesium alloy coupled with different alloys in Beijing atmospheric environment were investigated. The results show that the magnesium alloys act as anode. The atmospheric galvanic effect of magnesium alloys coupled with LY12 aluminium alloy is the least in all of testing cathode alloys. The atmospheric galvanic effects in Beijing compared with other cities indicate that atmospheric environment is the most important factor. The atmospheric galvanic effects for magnesium alloys are affected by cathode alloy, testing time, sample size and environment condition. SEM, XRD and optical microscope were used to investigate the morphology changes on the surface of AM50 magnesium alloy.