The combustion processes in utility boilers must be carefully controlled to improve the combustion efficiency and operating stability, especially at low operating loads. The gas temperatures and various gas concentrations were experimentally measured and numerically simulated in a 200MW swirling fired pulverized coal boiler with radial bias combustion burners at various operating loads (100%, 65% and 52%). The Inter-phase Slip Algorithm model was used for the two-phase flow with comprehensive coal combustion models used for the combustion process. The simulation results agree well with experimental data and show that high pulverized coal concentration and high temperature zones form at the swirl burner outlets which improve coal ignition and stable combustion. With the operating load decreased from 100% to 52%, the observed furnace flame was stable without extra oil injection. Although the temperature in the upper burner area decreased from 1476oC to 1318oC due to the coal supply shutdown of the upper burners, the temperature in the lower burner area increased slightly from 1336oC to 1350oC which guaranteed stable combustion in the furnace. The CO concentrations were lower in the center region at the furnace exit due to the higher gas temperatures in the center region which promoted further CO oxidization reactions. The average oxygen concentration at the furnace exit was about 7.2% and that of CO was about 48 mg/kg at 65% operating load. It indicated that the radial bias combustion swirl burners provide good operating stability and high combustion efficiency at various operating loads.