The invention discloses zinc powder slurry for improving secondary adhesive force of a waterborne epoxy zinc-rich coating. The zinc powder slurry is prepared from, by weight, 10-15 parts of modified amine curing agents, 5-10 parts of PM (particulate matters), 1-3 parts of dispersing agents, 0.5-1 part of wetting agents, 2-4 parts of silane coupling agents, 1-2 parts of anti-settling agents and 70-80 parts of zinc powder. According to the zinc powder slurry, the silane coupling agents and zinc powder are dispersed and wet in advance, good wet adhesive force is formed, and the secondary adhesiveforce of a coating film can be greatly improved. The invention further discloses a coating process of the zinc powder slurry for improving the secondary adhesive force.