The present invention relates to a carbon nanotube encapsulated cobalt and oxide (CoO and Co3O4) nanosphere absorbing material thereof and a preparation method thereof, and belongs to the electromagnetic wave absorbing material technology field. The micro-morphology of the absorbing material is a hollow rhombic dodecahedron structure composed of the carbon materials, the carbon nanotubes grow on the surface of the rhombic dodecahedron structure, and a cobalt and an oxide nanosphere thereof are encapsulated at the end at the outer side of each carbon nanotube. The size of the rhombic dodecahedron structure is 400-550nm, the external diameter of each carbon nanotube is 14-16 nm, and the internal diameter is 11-13 nm; the diameters of the cobalt and the oxide nanosphere thereof are 11-13 nm,the proportion of the amorphous carbon and the graphitized carbon in the absorbing material is 1: 0.79-1.17, and the saturation magnetization intensity of the absorbing material is 27.83-39.4 emu/g; the maximum electromagnetic wave absorption exceeds -40 dB, and an effective absorption range exceeds 4.5 GHz. After using the 1M sulfuric acid or 1M ammonia to process 6-12 hours, the maximum electromagnetic absorption of the absorbing material still exceeds -40 dB, and the effective absorption range exceeds 4.5 GHz, thereby having the immense potential at the aspect of the electromagnetic wave absorbing material.