The invention relates to the technical field of preparation of wave-absorbing materials, in particular to a preparation method of a high temperature resistant wave-absorbing material. According to thepreparation method, the wave-absorbing material with the high temperature resistance and a good wave absorbing property is prepared by taking carbon fibers as a substrate, polyimide resin and siliconcarbide and the like as a fortifier, and silica sol and dextrin as a modifier, silica gel can effectively isolate preventing contact of oxygen in air from getting in contact with and carbon fibers inair, accordingly the high temperature resistance of the wave-absorbing material is improved, absorbing of electromagnetic waves can be achieved by the modified carbon fibers, microwave absorption ofthe wave-absorbing material is enhanced, meanwhile, through blending and fermentation of polyimide resin and plant oil and yoghourt, an ester group is stem-grafted on the surface of resin under self cross-linking effect of microbes, the compatibility of resin and carbon fibers is improved, silicon carbide, hexagonal boron nitride, dextrin and aluminum oxide are added continuously, the wave absorption performance of the wave-absorbing material can be improved, and therefore, the preparation method has a wide application prospect.