As an advanced power generation system, supercritical CO2 (S-CO2) coal fired power plant has advantages of high electric efficient and compact system layout. In this paper, the coal combustion characteristics and NOx formation in coal-fired S-CO2 boiler has been explored by numerical simulation. The boiler wall temperature distributions were determined according to the 1/8 partial flow strategy for S-CO2 coal-fired power plant. The effect of SOFA ratio on the gas flow field, the gas temperature, the species concentration including NOx distribution was investigated. The results show that the SOFA ratio has a great influence on the coal combustion process and NOx formation. With the increase of SOFA ratio, the O-2 concentration decreases in the main coal burning zone, a higher CO concentration can be found. A lower gas temperature zone in the main burning zone and a lower NOx emission near the furnace outlet can also be observed with a higher SOFA ratio. The results presented promote a better understanding of the NOx formation characteristics and would be benefit for the NOx control in coal-fired S-CO2 boiler. (C) 2019 Elsevier Ltd. All rights reserved.