Through a series of experiments and CFD numerical simulations of 130t/h pulverized-coal-fired furnace, the influences of deeply air staging firing on combustion pattern and NOx emission control were discussed in the present paper. The modeling results show the NOx emissions were effectively decreased by 36.4% with more separated-over-fire-air (SOFA) ratio feeding of 25%. The CFD modeling results were verified through the on-site operation data. Furthermore, the adverse issues were discussed regarding the highly air-staging technology. The predicted average combustion temperature in the burner zone of furnace was reduced by 120°C with comparison of different SOFA ratios increased, while the flue-gas temperature increased by 80°C above the SOFA nozzle. More CO emission occurs on the top of furnace. Ash slagging phenomena were observed during ash sampling near SOFA, as is due to unburned char with higher particle temperature and bigger tangential circle diameter of flame pattern on basis of modeling results.