Abstract: The spherical nickel nanoparticles (an average diameter of 70 nm) were prepared by the wire electrical explosion method，Fe₃O₄ was coated on nickel to form the complete coverage by the co-precipitation method，and the silane coupling agent 3-mercaptopropyltrimethoxysilane (HS-(CH₂)₃Si(OCH₃)₃，MPTS) was used as a primer to improve the nickel surface.The as-synthesized  Fe₃O₄/Ni composite particles were uniformly dispersed into the phenolic cement， then the mixture was pasted on the metal plate with the area of 200 mm×200 mm as the test board.The test of microwave absorption was carried out by the radar-absorbing materials (RAM) reflectivity far field radar cross-section (RCS) method. The results show that as a microwave absorber，the properties of the  Fe₃O₄/Ni nanoparticles with core-shell structure are superior to those of Ni nanoparticles or Fe₃O₄ nanoparticles at the same mass quality ratios. Furthermore，with the content of Ni increasing，the microwave absorption performances of the as synthesized  Fe3O4 /Ni nanoparticles are enhanced. At the same time，the absorption frequency ranges will shift to the high frequency sections when the contents of Fe₃O₄  increase. 