<p>The heavy metal Cr(VI) has caused serious impacts on human health and the ecological environment. To reduce the impact of Cr(VI), we prepared Fe³⁺-doped Bi₂MoO₆ using a hydrothermal method for the reduction of Cr(VI) to Cr(III). The effect of Fe doping on the structure, morphology, and properties of Bi₂MoO₆, and obtained the optimal doping amount of Fe³⁺. Fe ions doping can significantly reduce the bandgap, resulting in good visible-light absorption intensity and significantly expand the light absorption range. Fe–Bi₂MoO₆/Ppy heterojunctions were prepared by in situ polymerization deposition methods to improve their photo-reduction performance. During the reduction, the reduction rate of single Bi₂MoO₆ is 29.4%. When the Fe³⁺ doping amount is 1.0 wt%, the Cr(VI) reduction rate of 1.0Fe-Bi₂MoO₆ material is 33.6%, and the reduction efficiency is slightly improved. The Cr(VI) reduction rate of the 1.0Fe-Bi₂MoO₆/0.5Ppy composite photo-catalyst reached 92.5%, significantly improving the Cr(VI) reduction effect. Its corresponding reduction rate is 7.24 times that of Bi₂MoO₆ and 11.74 times that of Ppy. This work indicated that the construction of 1.0Fe–Bi₂MoO₆/0.5Ppy heterojunction is an effective approach to improve photocatalytic activity of Bi₂MoO₆ and efficiently reduce Cr(VI).</p>