Abstract: Co-firing pulverized coal with ammonia offers a promising low-carbon pathway for coal-fired power systems. Significant differences between NH₃ and coal in combustion reactivity, ignition characteristics, and nitrogen transformation pathways lead to notable impacts of co-firing strategies and operating parameters on NO_x formation. To investigate the coupling mechanisms and NO_x emission behavior, a 30 kW electrically heated one-dimensional furnace was established, enabling independent control of the ammonia-coal ratio, NH₃ injection position, and over fire air (OFA) ratio. Experiments systematically examined the effects of NH₃ injection location (0—0.6 m), blending ratio (0−50%), staged-air ratio, combustion temperature (1 100−1 300 ℃), and excess air coefficient on NO_x emissions.Results show that with simultaneous injection of coal and ammonia, NO_x emissions first rise and then decline with increasing NH₃ proportion at 1 100 ℃ and 1 200 ℃, accompanied by NH₃ slip at high blending ratios. At 1 300 ℃, NO_x increases monotonically with the NH₃ ratio. Temperature exerts a minor influence on NO_x at low NH₃ fractions. Higher overall excess air consistently promotes NO_x formation. Varying the NH₃ injection position significantly alters NO_x emissions. Injecting NH₃ downstream of the coal jet, where the local atmosphere is oxygen-lean and reducing, effectively reduces NO_x across a wide range of blending ratios. The suppression effect of air staging on NO_x depends on the NH₃ injection location, indicating a synergistic interaction between staged air and injection positioning for NO_x control.