The invention belongs to the technical field of functional materials and relates to a FeSiAl/ferrite composite wave-absorbing agent. According to the FeSiAl/ferrite composite wave-absorbing agent, theball milling process is adopted, the shearing and efficient impact effects among ball milling mediums is utilized, the surface of FeSiAl powder is coated with flake hexagonal crystal ferrite, and ferrite is spread along the surface of the flaky FeSiAl powder; the FeSiAl/ferrite composite wave-absorbing agent is characterized in that the flaky FeSiAl powder is coated with the ferrite, the thickness is less than or equal to 2 micrometers, the particle diameter D (n,50) is greater than or equal to 40 micrometers, and the apparent density is 1.0 g/cm<3>-1.5 g/cm<3>; the wet ball milling process is adopted for the preparation of the FeSiAl/ferrite composite wave-absorbing agent; and the material mass ratio of the ferrite to the FeSiAl ranges between 1:1 and 1:6. The FeSiAl/ferrite composite wave-absorbing agent provided by the invention has the advantages that the permittivity is low, the magnetic conductivity is high, and the impedance matching property is good; the wave-absorbing frequency band of a FeSiAl wave-absorbing material can be effectively broadened; and the FeSiAl/ferrite composite wave-absorbing agent is applicable to full-frequency-band wave-absorbing materials at the waveband of 1 GHz-12 GHz.