N-release and devolatilization from pulverized coal combustion was found to be different in different rank and composition of coal. It was investigated that nitrogen compound was included more in volatile than in char for sub-bituminous coal but reversed in bituminous coal. NOx emission was decreased with decreasing air ratio and with increasing volatile content in coal and volatile matter content produced to combustion in high temperature. In particular, effective NOx reduction was achieved with high temperature and fuel rich condition at the onset of combustion. Thus, staged combustion for NOx reduction was achieved by subsequent supply of air after maintenance to low air ratio in initial stage of combustion region.