•Fe3O4/rGO composites were prepared through a facile hydrolysis process.•The composites exhibit specific capacitance of 350.6 F g−1 at 1 mV s−1 and 157.6 F g−1 at 100 mV s−1.•The composites show much higher specific capacitances than either pure rGO or pure Fe3O4.•The good electrochemical performance can be attributed to the positive synergistic effect.Fe3O4/reduced graphene oxide (rGO) composites were prepared through a facile hydrolysis route and subsequent annealing process and used as the electroactive materials for supercapacitors. The as-prepared Fe3O4/rGO composites exhibit much higher specific capacitances than either pure rGO or pure Fe3O4, meanwhile, the electrochemical performance of Fe3O4/rGO composites with different amount of RGO has been compared. The optimized Fe3O4/rGO composites (FG-0.8) exhibit the highest specific capacitance of 350.6 F g−1 at 1 mV s−1, 157.6 F g−1 of the specific capacitance can still be retained when the scan rate increases 100 times to 100 mV s−1, indicating a good rate capability. These Fe3O4/rGO composites also show excellent cycling performance without any decrease of specific capacitance after 10,000 cycles. These fascinating performances can be attributed to the positive synergistic effect between Fe3O4 and rGO.