Lithium iron phosphate mixed with nano-sized acetylene black (LiFePO4-AB) was synthesized by a hydrothermal method and subsequent high-energy ball-milling process. Different contents of AB were added to improve the electronic conductivity of LiFePO4. The structural and morphological performance of LiFePO4-AB was investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope, and high-resolution transmission electron microscope. LiFePO4-AB/Li batteries were fabricated in an argon-filled glove box, and their electrochemical performance was analyzed by cyclic voltammetry and charge/discharge tests. The XRD results demonstrate that LiFePO4-AB has an olivine-type structure indexed to the orthorhombic Pnma space group. LiFePO4-AB/Li battery with 10 wt% AB shows the best high-rate discharge properties with the discharge capacities of 116 mAh g−1 at 1 C and 85 mAh g−1 at 10 C at room temperature.