The invention provides special waterborne air-dried primer for bridges. The special waterborne air-dried primer is prepared from specific components in weight proportion as follows: 50% of resin, 15% of pigments and fillers, 15.5% of methoxylated resin, 17% of deionized water, 0.5% of a dispersing agent, 0.1% of a wetting agent, 0.3% of a feeling agent, 1% of a PH regulator, 0.2% of a thickener, 0.3% of an adhesion promoter, 0.2% of a flash rust inhibitor and 0.1% of an anti-corrosive agent. According to the special waterborne air-dried primer for the bridges, part of pigments and fillers are added to water-soluble alkyd resin, so that the resistance of a paint film to corrosion, salt spray, water and alkali is enhanced, and the primer is applied to protective decoration of a bottom layer of each bridge in a seriously corroded atmospheric environment. The special waterborne air-dried primer for the bridges has great gloss, high hardness, excellent salt spray resistance, good resistance to water, alkali and acid and the like, the performance of the paint film has no obvious change after various performance tests, and the primer is non-toxic and environment-friendly.