Hydrogen　(H-2)　is　a　carbon-free　fuel　with　many　excellent　combustion　characteristics,　but　abnormal　combustion　is　one　of　the　main　obstacles　to　the　promotion　and　application　of　hydrogen-fueled　engines.　This　experimental　study　aims　to　investigate　the　suppression　of　the　heat　release　rate　(HRR)　of　a　hydrogen-fueled　engine　through　the　addition　of　ammonia　(NH3).　The　engine　was　run　at　1300　rpm,　with　manifold　absolute　pressure　(MAP)　of　61　kPa　and　NH3　addition　ratio　of　0%　and　2.2%,　under　lean-burn　conditions.　The　results　showed　that　the　addition　of　small　amounts　of　ammonia　reduced　the　combustion　rate　of　the　fuel　mixture,　prolonged　the　flame　development　period　(CA0-10)　and　propagation　durations　(CA10-90)　of　the　engine,　and　reduced　the　peak　in-cylinder　pressure　and　peak　HRR　under　lean-burn　conditions.　The　addition　of　ammonia　increased　the　peak　indicated　mean　effective　pressure　(IMEP)　and　the　peak　indicated　thermal　efficiency　(ITE)　of　the　engine.　The　addition　of　ammonia　resulted　in　increased　nitrogen　oxides　(NOx)　emissions.　(c)　2022　Published　by　Elsevier　Ltd　on　behalf　of　Hydrogen　Energy　Publications　LLC.