Well-crystallized, homogeneous nanocomposites of lithium iron(II) phosphate and carbon was synthesized by solid state reaction, and the obtained particles are spherical. Measurement of both CV and EIS shows that the lithium ion diffusion coefficient in the nanocomposites is affected by the incorporated carbon, and markedly increases with the carbon content. Meanwhile, the kinetics of lithium intercalation and de-intercalation is greatly ameliorated. These data provide strong evidence of the potential use of this kind of nanocomposite cathode in lithium ion battery.