The protection performance of four polymer/Dacromet composite systems, namely three solventborne polymers, polyurethane, alkyd primers and fluorinated polymer as well as a water - borne coating, styrene - acrylate latex, was studied with or without pretreatment by gamma - aminopropyltriethoxysilane（ γ- APS） by electrochemical impedance spectra（EIS） in 3.5 % NaCI solution. The results showed that the sequence of protective performance was： fluorinated polymer 〉 styrene - acrylate latex 〉 polyurethane 〉 alkyd/Dacromet composite system due to the different hydrophobic properties of organic polymers and existence of the dispersed micro - organic particles in styrene - acrylate latex. Pretreatment with γ- APS on Dacromet illustrated a markedly enhanced anti - corrosion performance of the polyurethane and alkyd/Dacromet systems because of the presence of the silane film restrained the diffusion of corrosive particles. But it also suppressed the synergetic protective effect in styrene - acrylate latex system, which led to decrease anti - corrosion performance. Pretreatment presented no obvious influence on fluorinated polymer/Dacromet system due to the good hydrophobic property ot： the polymer.