The invention relates to the technical field of wave absorbing materials. A preparation method of a wave absorbing material includes the steps of firstly, dissolving an organic
carbon source and
metal salt in
organic solvent, and conducting stirring to form a solution; secondly, soaking
polyurethane foam in the solution obtained in the first step, taking out the
polyurethane foam, repeatedly squeezing the
polyurethane foam through
filter paper, and placing the squeezed polyurethane foam with the solution in air to be dried; thirdly, cooling the dried polyurethane foam to the
room temperature after conducting temperature rising, oxidation and solidification on the dried polyurethane foam obtained in the second step under the
atmosphere of air; fourthly, conducting temperature rising and
carbonization on the oxidized and solidified polyurethane foam obtained in the third step under the protection of the
inert atmosphere, and cooling the polyurethane foam to the
room temperature so as to obtain the required target material. The preparation process which is adopted is easy to operate, high in carbon yield, short in reaction time and low in material cost and can be directly used for
microwave absorbing without conducting secondary
processing, and the product has the advantages of being small in density, wide in wave absorbing
frequency band, high in absorbing strength, resistant to the high temperature and the like.