Some previous studies have showed that water extract of Thai Nguyen green tea leaves (W(C)) inhibit corrosion for mild steel in acid solution. In this study, the authors separated W(C) into residures with the increasing polarization and used residures as corrosion inhibitor for mild steel in acid HCl solution. The result has defined main components of residures and the ability to inhibit corrosion for CT38 steel in 0,1 and 1M HCl solution of residures. Among them, the best ability to inhibit corrosion for CT38 steel in acid solution is the W residure.