The olivine-type samarium-doped LiFe1 − xSmxPO4/C (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) composites were synthesized via liquid-phase precipitation reaction combined with the high-temperature solid-state method. The structure, morphology, and electrochemical performance of the samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive spectroscopy, galvanostatic charge–discharge, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy. The results showed that the small amount of Sm3+ ion-doped can keep the olivine microstructure of LiFePO4, modify the particle morphology, decrease polarization overpotential and charge transfer resistance, and enhance exchange current density, thus improve the electrochemical performance of the LiFePO4/C. However, the large doped content of Sm3+ ion can form more SmPO4, which can weaken the electrochemical performance of LiFePO4/C. Among all the doped samples, LiFe0.99Sm0.01PO4/C showed the best rate capacity, cycling stability, and low temperature performance. The LiFe0.99Sm0.01PO4/C sample exhibited the initial discharge capacity of 148.1, 133.4, 117.5, and 106.6 mAh g−1 at 1C, 2C, 5C, and 10C, respectively. In addition, the discharge capacity of the material was 94.8 mAh g−1 after 800 cycles at 10C. Moreover, the initial discharge capacity of 0.1C, 0.2C, 0.5C, and 1C were 104.4, 96.2, 53.9, and 50.8 mAh g−1 at −20 °C.