A numerical simulation model was developed for an ammonia-diesel dual-fuel two-stroke low-speed marine engine by using the 3D simulation software Converge，and the accuracy of the model was also validated. The effects of two injector arrangements，namely close arrangement and uniform arrangement，and different fuel injection timing on engine performance and emissions were investigated under 112 r/min speed and 75% load operating conditions. The results show that the dual-fuel injector arrangement directly influences the fuel mixture formation and development，leading to different combustion modes and variations in engine performance and pollutant emissions. Under high-pressure direct injection dual-fuel conditions，NOx emissions are reduced by 45.71% to 59.63% compared to diesel-only operations，while greenhouse gas emissions are decreased by 91.38% to 98.12%. Advancing diesel injection timing to -4° CA facilitates faster ammonia ignition and combustion，but further advancing it to -6° CA shows an opposite trend. It is found that advancing liquid ammonia injection timing significantly improves work output，but NOx emissions increases. Delaying the liquid ammonia injection timing to 3° CA，NOx emissions reduces to below 3.4 g/(kW·h)，meeting the Tier Ⅲ emission regulation requirements.