Abstract: To investigate the NO_x formation characteristics of ammonia-hydrogen swirl premixed flames under acoustic excitation, hydroxyl radical plannar laser induced fluorescence (OH-PLIF) imaging technology was used to analyze the flame structure at the sound frequency of 180 Hz and the pressure amplitude of 200 Pa. Flame structure and surface density distribution were obtained through image processing techniques. The effects of combustion and acoustic field pulsation coupling on NO_x emissions under different equivalence ratios (Φ) and hydrogen blending ratios (Z_f) were explored. Results show that the acoustic field can suppress the formation of NO_x in ammonia-hydrogen swirl premixed flames to some extent, with the reduction effect influenced by Φ and Z_f. The acoustic field mainly affects the combustion flow field by creating periodic pulsating flows around the flame, thus demonstrating a better NO_x reduction effect in combustion fields dominated by air momentum at low equivalence ratios (Φ≤0.8). In combustion fields dominated by fuel chemical reactions at high equivalence ratios (Φ>0.8), the effect on NO_x emissions is less significant. Under the influence of the acoustic field, the surface density of lean flames increases, and the average OH intensity decreases, as the acoustic field enhances flame combustion intensity, accelerates the combustion rate, and improves heat and mass transfer with the surrounding flow field. When the hydrogen blending ratio is low (0.20≤Z_f<0.30), the acoustic field causes the flame area to shrink, leading to a relatively higher NO_x reduction. When the hydrogen blending ratio is high (0.30≤Z_f≤0.35), the compressive effect on the flame area weakens, and the NO_x reduction effect is slightly reduced.