Compared with thermally exfoliated graphene oxide (TEGO) prepared at high temperature of 800°C and a long time of 12h, microwave exfoliated graphene oxide (MEGO) is successfully synthesized at 800W for 2min benefiting from “inert and instant heating” of microwave irradiation and employed to optimize electrochemical performance of LiFePO4. The as-obtained LiFePO4/MEGO exhibits overwhelming superiorities to LiFePO4/TEGO, particularly in high-rate performance. Although LiFePO4/MEGO delivers the similar specific capacity of 158.1 mAh·g−1 as well as the LiFePO4/TEGO at the rate of 0.1C, the LiFePO4/MEGO performs smaller polarization of 53.3mV resulting in better specific energy of 518.1 Wh·kg−1 and energy efficiency of 89.8%. Even at the high rate of 10C and 20C, the LiFePO4/MEGO delivers excellent specific energy of 300.3 Wh·kg−1 and 229.7 Wh·kg−1 (with corresponding specific capacity of 104.3 mAh·g−1 and 87.3 mAh·g−1 respectively), much better than those of the LiFePO4/TEGO. After 2000 cycles, the LiFePO4/MEGO still performs excellent rate capabilities with 91.2% and 83.8% retention respectively.