This　study　aimed　to　modulate　the　magnetic　properties　of　selective　laser　melting　NiFeMo　alloy.　This　was　achieved　via　the　controlled　addition　of　Mo　elemental　in-situ　alloying　content　to　change　the　tissue　morphology　and　crystal　structure　of　SLM-formed　(NiFeMo)100_xMox　alloy　(x　=　0　wt%,　0.25　wt%,　0.5　wt%,　0.75　wt%,　1.0　wt%,　1.25　wt%,　1.5　wt%,　2.0　wt%).　The　results　of　scanning　electron　microscopy　(SEM),　X-ray　diffraction,　electron　backscatter　diffraction　(EBSD),　DC　B-H　hysteresis　tester,　and　transmission　electron　microscopy　(Titan-G2)　indicate　that　all　samples　are　predominantly　face-centered-cubic　(FCC)　gamma-　(Ni,　Fe)　solid　solutions　and　typical　soft-magnetic　hysteresis　line　features.　However,　the　lattice　parameter　a　of　gamma-　(Ni,　Fe)　decreased　and　then　increased　with　increasing　Mo　content.　When　the　added　Mo　content　is　0-1.25　wt%,　the　Mo　particles　inside　the　(NiFeMo)100_xMox　alloy　become　nucleation　sites,　creating　a　diffusive　metallurgical　behavior　with　the　Ni　and　Fe　elements,　and　preventing　the　growth　of　columnar　crystals,　leading　to　the　reduction　of　LAGBs　density　and　the　enhancement　of　the　{111}　texture　orientation　in　the　easy　magnetization　direction,　increasing　Bs　and　the　decrease　of　Hc　of　the　NiFeMo　alloy.　At　the　Mo　content　of　1.25　wt%,　the　soft　magnetic　properties　were　optimal,　with　Bs　and　Hc　being　0.704　T　and　17.31　A/m,　respectively.　Conversely,　when　the　added　Mo　content　was　1.5-2.0　wt%,　the　solubility　of　Mo　elements　in　the　gamma-　(Ni,　Fe)　solid　solution　was　limited,　which　resulted　in　the　occurrence　of　metallurgical　defects　within　the　organization　such　as　unfused　Mo　particles,　unfused　areas,　and　porosity.　Moreover,　when　the　added　Mo　content　increased　to　2.0　wt%,　the　{111}　lattice　spacing　in　the　easy　magnetization　direction　increased　by　0.2261　nm　compared　to　the　NiFeMo　alloy,　and　the　average　lattice　distortion　Delta　epsilon　increased　to　0.16%,　causing　a　decrease　in　the　soft　magnetic　performance　of　the　(NiFeMo)98Mo2　alloy,　with　Bs　reducing　to　0.6666　T　and　Hc　increasing　to　23.44　A/m.