The invention discloses a capacitor carbon/lithium iron phosphate composite material, a preparation method thereof and a lithium-ion capacitor battery using the same as a cathode material and relates to a lithium iron phosphate material, a preparation method and a lithium-ion capacitor battery using the lithium iron phosphate material as a cathode material, solving the problems of higher preparation cost of the traditional lithium iron phosphate and poor high-magnification charge/discharge properties of the lithium-ion batteries prepared from the traditional lithium iron phosphate. The composite material is formed by loading the lithium iron phosphate on activated carbon. The preparation method comprises the following steps of: preparing a lithium iron phosphate precursor by using a trivalent ferric salt, a phosphorus compound, a lithium source compound and an organic micromolecule carbon source as raw materials; and then mixing the precursor with the activated carbon and sintering. In the invention, the cathode sizing agent of the lithium-ion capacitor battery comprises the capacitor carbon/lithium iron phosphate composite material, a conductive agent and a bonding agent; the particle size distribution of the composite material is uniform; the trivalent ferric salt is used as a raw material, and the cost on the preparation is low; and the capacitor battery has good charge/discharge cycle performances and the mass specific capacity larger than 60mA.h.g<-1> under 20C magnification.