Composites formed during the co-precipitation of ubiquitous dissolved organic matter (DOM) and Fe(III) in natural water systems might be potential scavengers for heavy metal. Despite this, little is known about how organo-Fe(III) composites (OFC) affects the fate of Cr(VI). In this study, we aimed to determine sorption and simultaneous reduction of Cr(VI) on OFC in relation to pH and C/(C+Fe) ratios of co-precipitation processes. Results showed the greatest Cr sorption of 51.8 mg g^-1 on the OFC sample precipitated at pH 3.0 and contained the C/(C+Fe) molar ratio of 0.71. Wherein the Cr(VI) removal subsequent to the co-precipitation was dominated by the sorption on Fe hydroxides. Although amounts of total sorbed Cr decreased with increasing C/(C+Fe) molar ratios, the reverse trend on Cr(VI) reducibility compensated the Cr(VI) removal capability of OFC samples. While OFC contained C/(C+Fe) ratios ≤ 0.87, Cr(VI) was mainly sorbed on ferrihydrite. However, the increasing amounts of co-precipitated OM that homogeneously distributed with Fe domains on OFC surfaces could trigger a pronounced Cr(VI) reduction as C/(C+Fe) ratios ≥ 0.89. Collectively, our results implied an alternative strategy for Cr(VI) remediation by controlling C/Fe ratios in suspensions. Therefore, a two-step processing for Cr(VI) removal was suggested to improve the removal efficiency for Cr(VI). After most of Cr(VI) was sorbed on Fe hydroxides, the remaining Cr(VI) could be reduce to Cr(III) by increasing C/Fe ratio in systems.