The work aims to chemically adsorb a layer of small insulating molecules on the surface of microwave absorbent to prepare a low frequency wave absorbent of low permittivity and high corrosion resistance. The particle surface of alloywas treated by mechano-chemical ball milling to enhance the chemical adsorption between behenic acid and the absorbent, so as to prepare a flaky Fe50Ni50@behenic acid composite absorbent with low permittivity, smooth surface, high grain orientation and corrosion resistance. The behenic acid coating could regulate the cold-welding effect among powder, induce the slipping of Fe50Ni50 powder along the {111} crystal planes, and promote the formation of {001} texture in the powder. At the same time, the insulated and hydrophobic behenic acid coating could prevent the formation of conductive network among powder and reduce the permittivity of flaky Fe50Ni50. Thus, the powder had low permittivity, high permeability and corrosion resistance. In conclusion, Fe50Ni50@behenic acid wave absorbent particles show good low frequency wave absorption and corrosion resistance, which provides a new idea for developing new wave absorbing materials with excellent environmental resistance and strong low frequency wave absorption ability.