Abstract: The challenges of inadequate combustion stability and excessive NO_x emissions remain critical bottlenecks for the utilization of ammonia as a zero-carbon fuel. Gliding arc plasma technology is employed to enhance the combustion performance of methane/ammonia premixed mixtures. The stability and emission characteristics of methane/ammonia/air premixed swirling flames are examined under various equivalence ratios （Ф） and ammonia contents （x_\mathrmNH_3 ）. Increasing ammonia contents raises the flame height and reduces flame stability, whereas the application of gliding arc plasma significantly improves stability. With x_\mathrmNH_3 ranging from 0 to 1.0, the use of gliding arc plasma extends the lean blow-off limit to 0.46−0.79 （an increase of approximately 10.2%−40.3%） and the rich blow-off limit to 1.92−2.31 （an increase of approximately 28%−32%）. Spectral diagnostic indicate that the emission intensities of \mathrmH_\alpha^* , \mathrmOH^* and \mathrmNH_2^* active species increase with ammonia content, promoting combustion. The \mathrmNH_2^* species play a major role in reducing NO_x emissions during combustion. At Ф=1.1 and low ammonia contents （x_\mathrmNH_3 ＜0.6）, gliding arc plasma slight increases NO emissions, reaching a peak at x_\mathrmNH_3 =0.4 （an increase of about 9%） due to the elevated flame temperature and enhanced thermal NO_x formation. As x_\mathrmNH_3 increases further, gliding arc plasma strengthens the \mathrmNH_2^* -induced NO reaction pathways, achieving a maximum NO reduction of 15.5%. Reaction pathway analysis shows that ammonia is first converted to \mathrmNH_2^* , which subsequently participates in two competing processes: oxidation through the HNO intermediate to produce NO, or direct NO reduction to form N₂ and NNH. The negative sensitivity coefficient of NO confirms that \mathrmNH_2^* plays dominant role in NO reduction. Gliding arc plasma effectively enhances the stability of methane/ammonia premixed flames, extends the lean and rich flammability limits, and reduces NO_x emissions, providing a promising route for clean and efficient ammonia combustion.