The　contribution　to　fine　particulate　air　pollution　(PM2.5)　from　ammonia　emissions　has　been　proven　to　be　significant.　In　China,　agricultural　sources　contribute　to　the　majority　of　ammonia　emissions.　It　is　necessary　and　valuable　to　explore　air　quality　improvements　caused　by　the　mitigation　of　agricultural　ammonia　emissions.　The　purpose　of　this　study　was　to　quantify　the　reduction　effects　on　PM2.5　and　secondary　inorganic　aerosols　by　performing　air　quality　simulations　based　on　the　developed　agricultural　ammonia　emission　inventory　at　the　county-level　within　the　Beijing-Tianjin-Hebei　(BTH)　region.　The　results　demonstrated　that　the　total　NH3　emission　in　the　BTH　region　was　1625.03　Gg　in　2015.　Livestock　manure　spreading　represented　58%　of　the　total　emissions　(941.79　Gg　NH3),　while　synthetic　fertilizer　applications　accounted　for　the　remaining　42%　of　the　emissions.　Spatially,　the　agricultural　ammonia　emissions　were　generally　distributed　over　the　southern　BTH　regions　(Handan　and　Shijiazhuang)　due　to　the　intensive　agricultural　activities　in　this　area.　Temporally,　the　agricultural　ammonia　emissions　peaked　during　summer,　consistent　with　variations　in　temperature　and　agricultural　practices.　Compared　to　the　baseline　scenario,　the　annual　average　PM2.5　concentrations　in　the　BTH　region　were　reduced　by　2.57%,　5.08%,　and　5.71%,　respectively,　under　the　Progressive　(NH3　emission　cut　by　21.26%),　Stringent　(NH3　emission　cut　by　45.58%),　and　Complex　(NH3　emission　cut　by　46.63%)　scenarios.　Moreover,　under　the　same　conditions,　secondary　inorganic　aerosols　such　as　sulfate,　nitrate,　and　ammonium　were　alleviated　by　2.94-6.85%,　3.45-17.9%,　and　4.24-23.32%,　respectively.　The　results　confirmed　that　mitigating　ammonia　emissions　could　lead　to　the　considerable　reduction　of　nitrate,　followed　by　ammonium.　In　contrast,　the　impact　on　sulfate　was　relatively　limited.　This　study　could　provide　helpful　and　reliable　evidence　to　determine　effective　mitigation　measures　and　control　strategies　for　policy　makers.