Targeting at the poor physical shielding performance of the epoxy coating containing polyaniline, this paper aims to further improve the corrosion protection performance of epoxy coating containing polyaniline (PANI) on magnesium alloys by adding the flake graphite with lamellar structure into the coating. Firstly, PANI was synthesized on the surface of flake graphite via chemical oxidation polymerization. The synthetic PANI/flake graphite composite powder was characterized by X-ray diffractometer, scanning electron microscope and Fourier transform infrared spectrometer. Then different coatings were prepared on the surface of AZ91D magnesium alloy after the composite powder was dispersed evenly in epoxy resin. At last, the corrosion performances of different coatings in 3.5wt% sodium chloride solution was studied by electrochemical impedance test. The results indicate that PANI can be polymerized successfully on the surface of flake graphite, the adhesion of the epoxy coating containing polyaniline was slightly reduced with the addition of flake graphite, and there is no apparent effect on the hardness, flexibility and impact resistance of the coating, but the addition of flake graphite significantly increased the impedance value of the epoxy coating containing polyaniline. When the ratio of aniline to flake graphite was 1∶1, the impedance value of coating was 1.3×108 Ω.cm2 after being soaked in the solution for 1488 hours, and the coating had an excellent protection performance. However, with the extension of the soaking time, the impedance value of the coating was gradually higher than that of the other coatings when the ratio of aniline to flake graphite was 4∶1. After being soaked for 4008 hours, its impedance value was 1.6×108 Ω.cm2, and the coating still had a good protection performance. Therefore, it can be concluded that, after the addition of PANI/flake graphite composite powder in the epoxy coating, a better protection effect on magnesium alloy is achieved through the mechanism of the synergy between shield effect of flake graphite in the early stage and the long-term corrosion inhibition effect of PANI, and that the protection effect of this coating is related to the ratio of polyaniline to flake graphite.