NOVELTY - The method comprises mixing a carbon nanotube with polyvinyl alcohol solution in a weight ratio of 0.31-1.02, stirring and dispersing the mixture to obtain carbon nanotube suspension solution, mixing bivalent iron salt and trivalent iron salt solution with distilled water, where a ratio of the bivalent iron salt and the trivalent iron salt is 1:1.7-2, adding the bivalent iron salt and the trivalent iron salt with the carbon nanotube suspension solution to obtain mixed solution of carbon nanotube, and performing ultrasonic dispersion to the mixed solution of carbon nanotube.    USE - The method is useful for preparing iron oxide/carbon nanotube composite material, which is useful in lithium ion battery.    ADVANTAGE - The method is capable of simply preparing the iron oxide/carbon nanotube composite material in cost-effective manner.    DETAILED DESCRIPTION - The method comprises mixing a carbon nanotube with polyvinyl alcohol solution in a weight ratio of 0.31-1.02, stirring and dispersing the mixture to obtain carbon nanotube suspension solution, mixing bivalent iron salt and trivalent iron salt solution with distilled water, where a ratio of the bivalent iron salt and the trivalent iron salt is 1:1.7-2, adding the bivalent iron salt and the trivalent iron salt with the carbon nanotube suspension solution to obtain mixed solution of carbon nanotube, performing ultrasonic dispersion to the mixed solution of carbon nanotube, adding sodium hydroxide with the distilled water to prepare sodium hydroxide solution, mixing the dispersed mixture and the sodium hydroxide solution by providing nitrogen protection function, electromagnetically stirring a mixture of the dispersed mixture and the sodium hydroxide solution at 50-80 degrees C, post-treating the mixture of the dispersed mixture and the sodium hydroxide solution, washing deposition on a magnet with distilled water and absolute ethyl alcohol, and drying the washed magnet to obtain nanometer iron oxide coated carbon nanotube magnetic composite material, where the magnetic composite material has a production rate of 12 V/minute, heating temperature of 280-300 degrees C and nitrogen protection time of 12 hours to improve stability of the magnetic composite material. The carbon nanotube is carboxyl functional group comprising a multi-wall carbon nanometer tube.