With the increasing demand for new energy consumption and the national target of double carbon reduction, the stable combustion of boilers under low load conditions is of great significance for the deep and flexible peaking operation of thermal power generatingunits. The numerical simulation and experimental verification of the combustion characteristics of a 660 MW supercritical wall type tangentially combustion pulverized coal boiler under multiple operating conditions at low load were conducted. The impact of different combustionstructures on the distribution characteristics of velocity, temperature, and oxygen concentration in the furnace were studied. By discretizingthe combustion zone with a refined mesh, the accuracy of the simulation results is improved. The deviation between the numerical simulation results and the experimental results is small, indicating that the simulation results are reliable. The results show that a good circularflow field of coal powder can be established and the residence time can be increased by opening the bottom burners and adjusting the airdistribution under 30% ultra-low load. Additionally, by properly increasing the distance between operating burners, the uniform distribution of heat load inside the furnace can be achieved, providing favorable conditions for the safe combustion of boiler under low load. Theexperimental results verify that the proposed combustion structure and operation strategy for the wall type tangentially fired boiler are reasonable, which can ensure stable combustion and meet various main steam parameters at 30% low load. The results can provide a basisand reference for the deep flexiblity operation of this type of ultra-supercritical unit.