In this study, the adsorptive and reductive mechanisms for decolorization of orange-colored G (OG) by Fe(Ⅱ)/goethite interfacial complex system were systematically investigated. The examined focuses were placed on the effects of pH values, and molar ratios of Fe(Ⅱ)/OG on the OG decolorization. The results show that surface-bonded Fe(Ⅱ) on goethite can effectively improve the rate of reductive decolorization. The reactions over the Fe(Ⅱ)/goethite complex system can be described well by the pseudo first-order kinetics. The increases in the solution pH and the capacity of absorbed Fe(Ⅱ) enhance the reaction rate of OG removal. Moreover, OG removal efficiency can reach 100% within 1 h in the presence of Fe(Ⅱ)/goethite complex system under basic medium condition where the Fe(Ⅱ) /OG ratio is 27.0 and the OG initial concentration is 50 mg/L. The efficient removal of OG is resultant from the synergistic effect of adsorption and reduction. The results achieved by the authors provide the theoretical guidance for pollution remediation in an anaerobic environment by effectively using the Fe(Ⅱ)/goethite complex system.