In this study, we report the effects of co-catalysts of Pt nanoparticles and Fe3O4 clusters on photocatalytic behaviors of g-C3N4 (CN) and the use of the resulting photocatalyst for CO2 photoreduction to solar fuels in a flow reactor operated at room-temperature. In presence of H2O vapors, the selectivity of photogenerated electrons was emphasized, and found that the yield rate and selectivity of CH4 were improved by deposition of Pt on CN. With further inclusion of Fe3O4 over Pt/g-C3N4 (PtCN), the CH4 yield rate was significantly enhanced and H2 formation inhibited simultaneously, resulting in improved CH4 selectivity. Results show that the optimized Fe3O4/ Pt co-decorated CN (0.50 %FPtCN) heterostructure possesses significantly enhanced CO and CH4 yield rates of 1.83 mu molg- 1h- 1 and 0.532 mu molg- 1h- 1, respectively, which were 9 and 38 times superior to pure CN, attributed predominantly synergistic effects of Pt, Fe3O4, and CN. Owing to exceptional conductivity and electron-sink function, Pt NPs are an excellent electron transporter, which facilitates interfacial charges transfer and prohibits their recombination, while, the Fe3O4 clusters can synergistically promote the CO2 photoreduction by effectively using electrons as the oxidation - reduction center. Finally, insight obtained from results is used to propose a possible underlying mechanism for superior photocatalytic performance.