As carbon-free and clean energy sources, the application of ammonia and hydrogen in fuel combustion is of great significance for the realisation of the strategic goal of "carbon neutrality". In this paper, the combustion characteristics of hydrogen-ammonia blended fuel in a micro gas turbine are investigated by numerical simulation, and the flow distribution characteristics, pressure loss, 𝑁𝑂𝑥 emission and fuel combustion velocity in the combustion chamber are analysed under different ammonia blending ratios. The results show that: the central reflux zone in the combustion chamber has a tendency of hysteresis and expansion due to the increase of the ammonia ratio; the pressure loss, 𝑁𝑂𝑥 emission and the exit exhaust temperature increase with the increase of the doping ratio; and the exit temperature distribution coefficient has a tendency of increasing and then decreasing with the increase of the doping ratio.