The　magnetic　property　of　soft　magnetic　material　is　much　dependent　on　its　shape　and　anisotropy.　In　this　work,　the　flake-like　FeNi3　particles　with　3D-network　structure　have　been　synthesized　through　hydrazine　reduction　at　ambient　condition　in　the　presence　of　sodium　lignosulfonate　(SLS).　The　morphology　and　crystalline　structure　of　the　FeNi3　nanoparticles　were　characterized　by　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　Transmission　electron　microscopy　(TEM)　and　energy　dispersion　spectrum　(EDS).　Both　of　the　static　and　dynamic　magnetic　property　of　the　FeNi3　particles　were　investigated.　The　results　indicated　that　the　morphology　of　the　FeNi3　particles　changed　from　spherical　to　flake　shape　with　increasing　SLS　concentration　or　reaction　time.　The　possible　mechanism　on　the　variation　of　particles　morphology　was　proposed.　The　static　magnetic　property　indicated　that　the　flake-like　FeNi3　showed　a　higher　saturation　magnetization　and　coercivity　than　that　of　the　spherical　particles.　Dynamic　magnetic　performance　showed　that　the　flake-like　FeNi3　particles　also　exhibited　significantly　higher　real　part　(μ＇)　and　imaginary　part　(μ＇)　of　the　complex　permeability　than　the　spherical　particles,　especially　in　the　range　0.6–1.0　GHz.　©　2021　The　Society　of　Powder　Technology　Japan