In this paper, the effects of immersion time on the electrochemical impedance spectroscopy model of nano-sized titanium modified epoxy coating immersed in 3.5(wt.%) sodilum chloride solution has been studied using electrochemical impedance spectroscopy(EIS). Through the analysis of the spectra of the coating at different immersion times, the results showed that the spectrum was different at the different immersion times. Therefore, the equivalent electrical circuit was varied with the increasing immersion time and there were the characteristics of the powder in the equivalent electrical circuits (electrochemical impedance spectroscopy model). By the study on the evlolution of impedance model in the given system, it was found that the nano-sized powder played an important part during the electrolyte diffusing to the surface of the substrate and the electrolyte reacting with the substrate