Magnetic　field　effects　(MFE)　of　ferromagnetic　spin　electrocatalysts　have　attracted　significant　attention　due　to　their　potential　to　enhance　catalytic　activity　under　an　external　magnetic　field.　However,　no　ferromagnetic　spin　catalysts　have　demonstrated　MFE　in　the　electrocatalytic　reduction　of　nitrate　for　ammonia　(NO3RR),　a　pioneering　approach　towards　NH3　production　involving　the　conversion　from　diamagnetic　NO3-　to　paramagnetic　NO.　Here,　we　report　the　ferromagnetic　Fe-TiO2　to　investigate　MFE　on　NO3RR.　Fe-TiO2　possesses　a　high　density　of　atomically　dispersed　Fe　sites　and　exhibits　an　intermediate-spin　state,　resulting　in　magnetic　ordering　through　ferromagnetism.　Assisted　by　a　magnetic　field,　Fe-TiO2　achieves　a　Faradaic　efficiency　(FE)　of　up　to　97%　and　an　NH3　yield　of　24.69　mg　mg(cat)(-1)　at　-0.5　V　versus　reversible　hydrogen　electrode.　Compared　to　conditions　without　an　external　magnetic　field,　the　FE　and　NH3　yield　for　Fe-TiO2　under　an　external　magnetic　field　is　increased　by　similar　to　21.8%　and　similar　to　3.1　times,　respectively.　In-situ　characterization　and　theoretical　calculations　show　that　spin　polarization　enhances　the　critical　step　of　NO　hydrogenation　to　NOH　by　optimizing　electron　transfer　pathways　between　Fe　and　NO,　significantly　boosting　NO3RR　activity.