Partial　pre-decomposition　of　ammonia　is　an　effective　means　to　improve　the　combustion　performance　of　ammonia.　This　work　conducts　numerical　simulation　on　an　ammonia　diffusion　combustion　device　based　on　ammonia　pre-decomposition　strategy.　The　effects　of　ammonia　pre-decomposition　ratio,　equivalence　ratio,　and　residual　heat　from　ammonia　pre-decomposition　on　combustion　and　pollutant　emission　characteristics　are　analyzed.　As　the　ammonia　pre-decomposition　ratio　increases,　the　flame　temperature　increases,　the　high-temperature　zone　of　the　flame　moves　closer　to　the　nozzle,　and　the　NOx　emissions　decrease.　NO　emission　dominates　in　NOx　emissions,　increasing　first　and　then　decreasing　as　the　equivalence　ratio　increases.　N2O　emission　mainly　occurs　under　low　ammonia　pre-decomposition　ratio　and　low　equivalence　ratio　conditions,　and　hardly　exists　after　the　ammonia　pre-decomposition　ratio　reaches　over　50%.　Preheating　fuel　with　residual　heat　from　ammonia　decomposition　can　stabilize　combustion　and　significantly　decrease　ammonia　leakage　without　increasing　NOx　emissions　when　the　ammonia　pre-decomposition　ratio　does　not　exceed　30%.　This　study　shows　that　increasing　the　ammonia　pre-decomposition　ratio　and　equivalence　ratio　can　effectively　improve　the　combustion　and　pollutant　emission　characteristics　of　ammonia,　and　the　residual　heat　from　ammonia　decomposition　should　be　fully　utilized　under　small　proportion　ammonia　pre-decomposition　conditions.　©2025　Chin.Soc.for　Elec.Eng.