Abstract: An analysis was performed to the retrofit schemes for low-NO_x combustion of a 350 MW pulverized coal-fired boiler, while numerical simulations were conducted to study the gas velocity field, in-furnace temperature field and the NO_x emission under different working conditions, following which the simulation results were compared with actual measurements. Results show that the NO_x emission may be reduced by extending and regulating the secondary air cone of swirl burner; to facilitate the NO_x reduction, enhance the flue gas temperature control at furnace outlet and to relieve the coking status, it is recommended to change the structure of over fire air (OFA) nozzle and increase the OFA flow rate, so as to keep the main combustion zone in the reduction atmosphere. The simulation results are proved to agree well with acutal measurements.