Lithium iron phosphate (LiFePO_4) was a cathode material of Li-ion battery. Its two synthetic methods of solid-reaction at high temperature and hydrothermal method were introduced. Its crystal structure,charge and discharge performance and cycling behavior were also presented. The effect of the conductive material,carbon black on the conductivity and the particle size of LiFePO_4 and the researches on doping were chiefly introduced.