The　synthesis　of　size-controlled　Sm2Fe17　magnetic　particles　is　a　prerequisite　for　the　fabrication　of　high-performance　Sm2Fe17N3　permanent　magnetic　materials.　Here,　Sm2Fe17　was　synthesized　using　a　cost-effective　reduction-diffusion　method.　The　calcium　chloride　molten　salt　was　introduced　to　control　the　particle　size　and　achieve　a　single　phase　of　Sm2Fe17.　The　effects　of　reduction-diffusion　reaction　temperature　and　the　amount　of　added　calcium　chloride　on　the　phase　constitution　and　microstructure　of　the　final　product　of　reduction-diffusion　were　systematically　investigated.　Adding　an　appropriate　amount　of　calcium　chloride　can　effectively　inhibit　the　overgrowth　and　sintering　of　the　reduced　particles.　By　employing　the　strategy　of　adding　20　wt%　of　calcium　chlorides　into　the　green　compacts,　we　were　able　to　successfully　synthesize　uniform　Sm2Fe17　particles　that　are　well-dispersed,　with　an　average　size　of　2.2　μm.　Furthermore,　by　combining　the　optimal　reduction-diffusion　conditions　and　the　nitriding　process,　the　hard　magnetic　Sm2Fe17N3　material　was　successfully　obtained.　This　study　could　be　useful　for　the　development　of　high-performance　Sm2Fe17N3　magnetic　materials　utilizing　reduction-diffusion　technology.　©　2023　Chinese　Society　of　Rare　Earths