The present disclosure discloses a waterborne epoxy resin for an anti-corrosion coating, and a preparation method and use thereof. In the preparation method, a strongly-hydrophilic polyethylene glycol (PEG) branch is introduced into a molecular chain of epoxy resin to realize the self-emulsification function of epoxy resin. Moreover, due to the short molecular chain, a solid content can reach up to 66.7% under the action of PEG. In addition, the waterborne emulsion can be prepared without adding any additional alcohol-soluble solvents and other high-boiling-point organic solvents, and a production process and a product use process both are very environmentally friendly. The waterborne epoxy resin can be mixed with a waterborne ammonia curing agent to form a film for corrosion protection.