This study aims to investigate the combustion characteristics of a premixed swirl flame for a fuel mixture made of ammonia and hydrogen. The use of NH3 and H2 as carbon-free fuels in combustion systems can significantly reduce greenhouse gas emissions. Blending ammonia with hydrogen is a promising approach to enhance hydrogen combustion safety and ammonia combustion intensity. A three-dimensional large eddy simulation using a DTF model was run in order to get extensive and multi-scale information regarding the flow and reacting field of a premixed swirl flame using a 50% NH3/50% H2 fuel blend. The findings indicate that whereas NO is created near the flame front, OH radicals are mostly synthesized in the inner recirculation zone. The fuel-NO pathway, which is sensitive to flame temperature, is what causes NO to be produced. The flame position is where the recirculation zone lies, and the total recirculation strength is determined by the inner recirculation strength. The prediction of NO concentration by LES, considering heat loss, is closer to the experimental value. The chemically reacting network simulation can precisely estimate NO emission by considering the heat loss ratio and the recirculation strength calculated by LES. Overall, this study provides valuable insights into the combustion characteristics of an ammonia/hydrogen fuel blend, which could contribute to the development of cleaner and more efficient combustion technologies. The findings of this study can be of great significance in the fields of sustainable energy and environmental protection.