The invention relates to waterborne epoxy heavy anti-corrosion coating and a preparation method thereof. The invention belongs to the technical field of anticorrosive coating. The coating comprises afirst component and a second component, wherein the first component comprises, by weight, 1 part of a modified waterborne epoxy emulsion, 0.1 to 0.3 part of deionized water, 0.005 to 0.01 part of modified graphene, 1.15 to 1.56 parts of a pigment filler, 0.02 to 0.03 part of a defoaming agent, 0.01 to 0.02 part of a dispersing agent, 0.01 to 0.02 part of a leveling agent, 0.03 to 0.05 part of an anti-flash-rust agent, 0.03 to 0.05 part of a sterilizing agent and 0.01 to 0.05 part of a thickening agent. The coating has good physical and chemical properties, coatings can resist to 1-degree bending without cracks, the impact resistance is 50 cm, the adhesive force is larger than or equal to 10 MPa, and coatings can resist a 5% NaOH solution, a 5% H2SO4 solution and 5% NaCl for 30 days under the normal temperature condition without blistering, cracking and falling off.