The invention discloses waterborne antirust paint and a preparation method thereof. The waterborne antirust paint is prepared from, by mass, 10-25 parts of waterborne acrylic acid modified epoxy ester, 0.6-1.2 parts of neutralizer, 20-30 parts of deionized water, 0.5-1.5 parts of dispersing agents, 0.2-0.5 part of defoaming agent, 14-18 parts of iron oxide red, 2-4 parts of mica powder, 6-10 parts of modified zinc phosphate, 10-14 parts of precipitated barium sulphate, 1-2 parts of propylene glycol, 10-15 parts of styrene-acrylic emulsion, 0.5-1.0 part of coalescing agent, 0.5-1.0 part of waterborne flush rust prevention agent, 0.5-1.5 parts of thickening agents and 0.2-0.5 part of mildew prevention agent. The waterborne antirust paint is high in film hardness, good in adhesive force and excellent in corrosion-resistant performance and mechanical performance, dryness and initial water resistance of paint films are remarkably improved due to the addition of styrene-acrylic emulsion, and the flush rust restraining performance of paint films is improved due to the addition of the waterborne flush rust prevention agent. Water serves as the diluent for the waterborne antirust paint, VOC emission in production and construction projects is greatly reduced, and the waterborne antirust paint is safe, environmentally friendly and capable of being widely used for paint coating on the aspects of steel structures, pipelines, automobile parts and the like.