NiFeMo　alloy　formed　using　additive　manufacturing　techniques　with　high　saturation　magnetic　induction　(BS)　and　low　coercivity　(HC)　are　crucial　in　aerospace　applications.　In　this　study,　we　successfully　formed　Cu-modified　(NiFeMo)100-xCux　alloys　via　in-situ　alloying　selective　laser　melting　(SLM).　The　effect　of　in-situ　alloying　Cu　content　on　the　microstructure　and　magnetic　properties　of　SLM-formed　NiFeMo　has　been　investigated,　and　efforts　have　been　devoted　to　developing　new　technologies　for　modulating　the　properties　of　SLM-formed　magnetic　materials.　The　microstructure　and　magnetic　properties　of　the　alloy　samples　were　analyzed　using　scanning　electron　microscopy　(SEM),　X-ray　diffraction　(XRD),　electron　backscattering　diffraction　(EBSD),　DC　B[sbnd]H　hysteresis　loop　tester　(MATS-2010S),　and　transmission　electron　microscopy　(Titan-G2).　The　results　demonstrate　that　(NiFeMo)100-xCux　alloys　possess　an　FCC　γ-(Ni,　Fe)　solid　solution　structure　within　the　range　of　added　Cu　content　in　this　study.　In　the　central　region　of　the　melt　pool,　columnar　crystals　grow　in　the　direction　of　the　temperature　gradient,　and　the　average　grain　size　(D)　decreases　gradually　with　increasing　Cu　content　from　in-situ　alloying.　Cu　atoms　induced　changes　in　the　crystal　structure　by　displacing　atoms　in　the　γ-(Ni,　Fe)　solid　solution,　resulting　in　lattice　distortion.　The　(NiFeMo)98Cu2　alloy　exhibited　an　average　crystal　plane　spacing　d　of　about　0.2261　nm　along　the　(11¯1¯)　γ-(Ni,　Fe)　direction　and　a　lattice　distortion　∆Ε　of　about　1.09　%.　The　saturation　magnetic　induction　varied　with　increasing　Cu　additions,　exceeding　0.7　T　for　NiFeMo　alloy　with　Cu　additions　of　0.8　wt%,　1.1　wt%,　and　1.4　wt%.　The　coercivity　generally　decreased　with　increasing　Cu　content,　attaining　values　below　17　A/m　when　Cu　(x　=　0.5　wt%,　0.8　wt%)　was　added　to　the　NiFeMo　alloy.　Therefore,　controlling　the　in-situ　alloying　Cu　content　within　the　range　of　0.8–1.4　wt%　is　beneficial　for　enhancing　the　soft　magnetic　performance　of　the　SLM-formed　NiFeMo　alloy.　©　2024　Elsevier　Inc.