Abstract: Based on actual velocity field and NO_x concentration distribution on the inlet cross section of selective catalytic reduction (SCR) system in a 1 000 MW coal-fired boiler, CFD-based numerical simulations were carried out to determine the outlet parameters by integrating the turbulence flow, multiple species transport and chemical reactions in the SCR system. Subsequently, an optimal ammonia injection strategy was acquired through repeated calculations according to the consistent distribution theory of ammonia-nitrogen ratio, which was validated through on-site experiments. Results show that spraying ammonia uniformly under the uneven inlet conditions would bring out prominent deviation of ammonia-nitrogen ratio at the inlet and of ammonia distribution at the outlet, causing serious NH₃ escape. On-site validation experiments prove the strategy to be effective in optimizing ammonia spraying, which helps to reduce the blindness of ammonia injection adjustment and improve the on-site efficiency of the system.