The invention discloses a preparation method for a scale-like nanocrystalline high temperature microwave absorbent, and belongs to the field of microwave absorption. The preparation method mainly comprises the following steps: spherical FeCo powder is prepared by adopting the gas atomization process, and is subjected to mechanical ball milling to obtain scale-like nanocrystalline FeCo powder. The FeCo absorbent prepared through the preparation method has the characteristics of high magnetic conductivity, high saturation magnetization, high Curie temperature and low dielectric constant, and can be used for 2-10Ghz of wave-absorbing materials at the room temperature of no greater than 600 DEG C. The preparation method has the advantages that the process is simple, the cost is low, and the preparation method is suitable for volume production, and has a wide application prospect.