PUF/PANI-C.O. double-walled microcapsules were prepared by in-situ polymerization and physical deposition method using castor oil (C.O.) as core material, urea-formaldehyde resin (PUF) and polyaniline (PANI) as wall materials, and added to waterborne epoxy coating (WEC) to prepare PUF/PANI-C.O./WEC composite coating. The composition and morphology of PUF-C.O. single-walled and PUF/PANI-C.O. double-walled microcapsules were characterized by FTIR, XRD and SEM. In addition, the corrosion behavior of microcapsule modified waterborne epoxy composite coating was studied by electrochemical impedance spectroscopy (EIS) and salt spray test. The results showed that PANI was successfully coated on the surface of PUF-C.O.single-walled microcapsules to form PUF/PANI-C.O.double-walled microcapsules. Compared with pure WEC and PUF-C.O./WEC, PUF/PANI-C.O./WEC exhibited more positive corrosion potential (~0.15 V) and higher low-frequency impedance value (~109 Ω·cm2) in long-term corrosion test, and the corrosion degree of the metal matrix was the lightest, showing the best corrosion resistance.