Pressurised oxy-fuel combustion (POFC) is a clean and efficient combustion technology with great potential. Due to the recycling of flue gas, the volume fraction of steam in flue gas is higher than that of conventional combustion, which enriches the free radical pool in the flue gas and thus affects the coal combustion process as well as the emission of gaseous pollutants. POFC experiments of coal and its volatiles were carried out in a fixed bed reactor, and the migration mechanism of volatile-N was studied in conjunction with chemical kinetic modeling. The results indicate that the synergistic effect of pressure and steam can significantly influence the combustion process, the combustion time is shorten, the volume fraction of CO is reduced in the exhaust gas and the combustion efficiency is improved. The volatile nitrogen comes from the pyrolysis of part of pyrrole, pyridine, and all quaternary nitrogen in coal. The higher pressure affects the main reaction pathway of NO formation, enhances the overall NO reduction and ultimately suppresses NO emission.