This study conducted co-firing experiments of NH3 and coal in a circulating fluidized bed combustor. The effects of NH3 co-firing ratio and combustion atmosphere of NH3 addition position on temperature, flue gas emissions, carbon content of the fly ash, NH3 content in fly ash were investigated. Results showed that NOx and N2O emissions increased with NH3 ratio increasing when adding NH3 in the reducing zone. A lower NOx increment was found within 0∼20 % NH3 ratio, increasing by 0.6 times compared to coal combustion. The NH3 content in fly ash was 2.74 mg/kg when NH3 ratio was 10 %. Compared to the reducing zone, adding NH3 into the oxidizing zone promoted the generation of more NOx and N2O, and simultaneously was detrimental to the burnout of NH3 and CO. Based on these findings, NH3 added in the reducing zone emerges as an optimized choice when NH3 and coal are co-fired in circulating fluidized bed. Extending the retention time of NH3 in the reducing zone was beneficial for controlling NOx and N2O, as well as promoting the burnout of NH3 and CO. Furthermore, fuel-N conversion analysis showed that over 96 % fuel-N was converted into harmless N2 when NH3 ratio exceeds 10 %.