6005A aluminum alloys were welded at different relative humidity conditions. The effects of relative humidity on the salt fog corrosion of the welding joints were researched. The results showed that the weight loss of the joints after 14 days corrosion was higher than that corroded after 7days, but the corrosion rate was lower. The corrosion rate first increased then declined with the increase of environmental humidity for the joints corroded for 7days. However, when the environmental humidity was 80%, corrosion rate achieved the maximum, when environment humidity was 70%, corrosion rate was the lowest. After corroded for 14 days, corrosion rate was the maximum when the environmental humidity was 50%, and it was the lowest when the environmental humidity was 90%. The tensile strength declined obviously after corrosion.