Oxy-steamcombustion is a promising next-generation combustion technology. Conversions of fuel-N, volatile-N, and char-N to NO and N2O during combustion of a single coal particle in O-2/N-2 and O-2/H2O were studied in a tube reactor at low temperature. In O-2/N-2, NO reaches the maximum value in the devolatilization stage and N2O reaches the maximum value in the char combustion stage. In O-2/H2O, both NO and N2O reach the maximum values in the char combustion stage. The total conversion ratios of fuel-N to NO and N2O in O-2/N-2 are obviously higher than those in O-2/H2O, due to the reduction of H2O on NO and N2O. Temperature changes the trade-off between NO and N2O. In O-2/N-2 and O-2/H2O, the conversion ratios of fuel-N, volatile-N, and char-N to NO increase with increasing temperature, and those to N2O show the opposite trends. The conversion ratios of fuel-N, volatile-N, and char-N to NO reach the maximum values at = 30 vol% in O-2/N-2. In O-2/H2O, the conversion ratios of fuel-N and char-N to NO reach the maximum values at = 30 vol%, and the conversion ratio of volatile-N to NO shows a slightly increasing trend with increasing oxygen concentration. The conversion ratios of fuel-N, volatile-N, and char-N to N2O decrease with increasing oxygen concentration in both atmospheres. A higher coal rank has higher conversion ratios of fuel-N to NO and N2O. Anthracite coal exhibits the highest conversion ratios of fuel-N, volatile-N, and char-N to NO and N2O in both atmospheres. This work is to develop efficient ways to understand and control NO and N2O emissions for a clean and sustainable atmosphere. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.