Oxy−fuel (O2/CO2) combustion technology shows great potential for carbon reduction. However, difference in the combustion atmosphere would affect coal combustion characteristics and pollutant emissions. In order to explore oxy−fuel combustion characteristics, two typical Chinese coals, sub−bituminous and lean coal, were utilized. Based on thermogravimetry and pilot−scale test, the ignition and burnout characteristics under oxy−fuel and air combustion atmosphere were investigated. Besides, the NOx emission characteristics were also investigated on the pilot−scale test. Through experimental results, these two kinds of coal showed different combustion characteristics, mainly due to differences in coal quality. Compared with air combustion, oxy−fuel combustion affected the coal combustion process. Firstly, the ignition temperature of sub−bituminous and lean coal decreased from 418 and 477 °C to 405 and 415 °C, respectively; the burnout temperature also decreased from 855 and 985 °C to 808 and 838 °C, respectively. Then, coal combustion performance was evaluated by comprehensive combustion characteristics (S); with an increase in S from, respectively, 3.659 and 2.013 to 4.826 and 3.545 × 10−8(min−2 × K−3), the combustion performance significantly improved. Then, the char burnout time was advanced for 1~3 min. Similar results were obtained on the pilot−scale test. The ignition temperatures decreased from 505 and 552 to 490 and 512 °C, respectively. Moreover, the char burnout rate increased by 0.5~5% and 2~11%, respectively. Lastly, the NOx concentration in flue gas was 2.2~2.6 and 2.0~2.3 times higher for the two kinds of coal under oxy−fuel combustion.