Effect　of　volume　ratio　V(NH3)/V(H2)　on　the　solid-gas　reaction　synthesis　of　Fe4N　was　investigated　by　the　thermodynamic　calculation　and　experimental　validation.　The　results　show　that　pure　Fe4N　can　be　synthesized　by　controlling　V(NH3)/V(H2)　within　a　wide　temperature　range.　And　when　V(NH3)/V(H2)=1:1,　the　reaction　temperature　has　the　largest　range　of　about　500-700　°C.　Moreover,　as　V(NH3)/V(H2)　increases/decreases,　the　temperature　decreases/increases　simultaneously　followed　by　the　continuous　decrease　of　temperature　range　until　the　temperature　reaches　zero.