In the global trend of carbon reduction, it is necessary to develop ammonia combustion technology. The research results of chemical kinetic mechanism of ammonia oxidation, laminar flow combustion rate and ignition delay time from domestic and foreign scholars were reviewed. For the problems of slow combustion rate and high NO_x emission in ammonia combustion, three ammonia-enhanced combustion technologies such as blending combustion, oxygen-rich combustion and plasma-assisted combustion were introduced, and the effects of pressure and moisture on NO_x emission were elaborated. The current research status of ammonia fuel combustion in internal combustion engines was highlighted, and the problems that internal combustion engine fuel blended with ammonia fuel would cause power reduction and high NO_x emission of internal combustion engine were pointed out. However, increasing the compression ratio, adjusting the ammonia blending ratio and the fuel injection strategy could effectively improve the power and emission of internal combustion engines after blending ammonia.