The work aims to study the corrosion resistance of the modified coating by adding the mesoporous chitosan microspheres of sodium phytate (load corrosion inhibitor) to the water-based polyacrylate coating. The chitosan microspheres were prepared by W/O emulsion solidification method. The morphology of chitosan microspheres was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The sodium phytate (corrosion inhibitor) was loaded into chitosan microsperes by negative pressure impregnation and the load rate of corrosion inhibitor was studied by thermogravimetric analysis (TGA). The microsperes of load corrosion inhibitor were added to the water-based coating with the mass ratio of 5% and the corrosion resistance was studied by electrochemical impedance spectroscopy (EIS). The SEM image showed that the chitosan microspheres were of good spheronization and the size was 20~30 μm. The results of FT-IR and XRD showed that the chitosan was crosslinked by vanillin (cross-linking agent) through Schiff base reaction and hydrogen bond interaction, thus leading to the solidification of chitosan microspheres and the low level of crystalline. The TGA results showed that the load rate of sodium phytate was about 25.79%; the EIS results showed that the charge transfer resistance of the water-based polyacrylate coating modified by the chitosan microsperes of load corrosion inhibitor had been increased. The mesoporous chitosan in the water-based polyacrylate coating controls the release of the sodium phytate, thus improving the utilization rate of corrosion inhibitor, and the corrosion resistance of the modified coating is improved.