The combustion of municipal solid waste and ammonia based selective non-catalytic reduction (SNCR) process in a moving-grate incinerator was simulated based on the computational fluid dynamics method. The combustion characteristics, overall temperature level, NOX emission, NOX removal efficiency and NH3 slip were analyzed to determine the optimal SNCR injection positions, injection speeds and injection ratios. Results showed that there was no difference in the furnace temperature and O-2 concentration under different SNCR injection positions, speeds and ratios. Moreover, the temperatures of SNCR injection zones were in the SNCR reaction temperature range of 800 degrees C-1100 degrees C under different SNCR injection positions, speeds and ratios. Further, injection positions strongly affected NOX removal efficiency and NH3 slip. Ammonia should be injected in layer and in the front region within the suitable temperature range as much as possible. Furthermore, SNCR injection speed had an optimal speed, which was 13.80 m/s with NOX removal efficiency of 51.50% and NH3 slip of 11.08 mg/Nm(3). In addition, there was a strong impact on NOX removal efficiency and NH3 slip under different SNCR injection ratios. Increasing the ratio of SNCR-1 (the first row of SNCR) was conducive to the improvement of NOX removal efficiency. The best injection ratio was the ratio of 6: 3: 1 (SNCR-1: SNCR-2 (the second row of SNCR): SNCR-3 (the third row of SNCR)), where NOX removal efficiency was 53.10% and NH3 slip was 8.43 mg/Nm(3).