Waterborne epoxy coatings are one of the most popular environmentally friendly coatings, but their constituent components are complex and their stability is poor. In order to further improve the protective performance of the coating，the aging mechanism and failure process of waterborne epoxy coating were studied by simulating marine atmospheric environment through laboratory cyclic acceleration test. The cyclic accelerated test of immersion-UV/condensation-hygrothermal aging was designed to simulate the randomness of the natural environment. And the mixing method in the chemical formula problem was used to design the test time of each single factor in the cyclic test. Firstly, determine the test time of 1 cycle as 144 h. Then, the minimum test time of immersion, UV/condensation and hygrothermal aging test and their percentage in the total cycle time were determined to be 24 h(17%), 12 h(8%) and 48 h(33%). Finally, the matrix table was obtained by mixing method and substituted into the total cycle time for conversion to generate three groups of cyclic acceleration test environment spectrum under different time combinations. Cut the carbon steel into a sample with a size of 50 mm × 50 mm × 2 mm, and cleaned after sandblasting (Sa 2.5). The A and B components of the water-based epoxy coating were prepared according to the volume ratio of 1.35∶1 and then mixed with 10%~15% deionized water. After curing for 20~30 min, spray on the surface of the sample by air spraying. Apply the W-101 gravity spray gun in the experiment. Scanning electron microscope (ZEISS EV0 MA15) was used to observe the micro morphology of the coating surface, and analyze the structure of the coating. by a Fourier infrared spectrometer (TENSOR27) The electrochemical impedance spectroscopy was used to study the failure process of the coating, and the changes in the protective performance of the coating were studied by combining data such as gloss, color difference, hardness and adhesion. After the cyclic tests in three different environments, micropores and cracks appeared on the surface of the coating. The damage of coating was the most serious in Environment 1 (immersion 24 h-UV/condensation/72 h-hygrothermal aging 48 h), and the hardness decreased from 118 to 78.5, with no obvious change in adhesion. After 6 cycles, the gloss loss reached 55.8%, and the color difference reached 26.21, showing severe gloss loss and color loss. After the cyclic test, the low-frequency impedance decreased to 3.9×103 ?.cm2. The coating hardness in Environment 2(immersion 54 h-UV/condensation 12 h- hygrothermal aging 78 h) and Environment 3 (immersion 54 h-UV/condensation 42 h-hygrothermal aging 48 h) did not change significantly, and the adhesion of the coating first increased and then decreased. The degree of gloss loss and color loss of the coating in Environment 3 was greater than that in environment 2, and the grades were obvious gloss loss (level 3) and severe discoloration (level 5). After the test, the low-frequency impedance of the coatings in the two environments decreased to 2.7× 105 Ω.cm2. The aging mechanism of waterborne epoxy coating was the synergistic effect of water degradation caused by hydroxyl groups and photooxidation degradation caused by UV irradiation. The failure process was divided into three stages:coating absorbing water, coating/metal matrix interface corrosion and coating failure.