The two-dimensional (2D) ultrathin Mg-Al layered double hydroxide modified by magnetic Fe3O4 (Fe3O4/Mg-Al LDH) was successfully synthesized via the co-precipitation method. The Fe3O4/Mg-Al LDH not only exhibits superior separation efficiency of charge carriers but also possesses signally enhanced photocatalytic activity for CO2 reduction than Mg-Al LDH. The as-prepared Fe3O4/Mg-Al LDH affords the CO and CH4 generation rate of 442.2 mot g(-1) h(-1) and 223.9 mu mol g(-1) h(-1). The enhanced reduction CO2 activity mainly comes from synergetic effect of Fe3O4 and ultrathin Mg-Al LDH. And Fe3O4 can increase the separation efficiency of photogenerated electron-hole pairs, and ultrathin Mg-Al LDH can reduce the transmission resistance of charge carriers. Moreover, a detailed mechanism insight of Fe3O4/Mg-Al LDH for CO2 reduction is also investigated by a series of characterization methods and activity experiments. This work offers a simple and environment-friendly approach to develop recycled photocatalysts in CO2 reduction treatment. (C) 2019 Elsevier Inc. All rights reserved.