Uniform LiFePO4/C particles were prepared by a fast, facile, and environmentally friendly microwave-assisted low-heating solid-state reaction using different organic carbon sources. The particles are very uniform and are 50-80 nm in size. The effects of the carbon sources on the microstructure and electrochemical properties of LiFePO4/C nanoparticles were investigated by X-ray diffraction, transmission electron microscopy, and electrochemical measurements. The results showed that the LiFePO4/C nanoparticles prepared from citric acid as carbon source, which has good crystallinity and a narrow particle size distribution, provided an initial discharge capacity of 112 mAh g(-1) at 0.5 C with excellent capacity retention. These advantages, coupled with the simple and effective preparation method, render LiFePO4/C nanoparticles attractive for practical and large-scale applications.