The main problem in non-thermal plasma flue gas denitrification is overly high energy cost.However，if the conditional parameters are set appropriately the energy cost can be reduced to a lowest possible value.In these respects the effects of the SO2 content in the gas and the ammonia applied to the gas are widely noticed.In this work a CSTR model was adopted to simulate the chemical reaction processes in non-thermal plasma flue gas denitrification.It was proved in principle that the effects of SO2 and addition on energy reduction were not initiated by SO2，but contributed by the externally added NH3.Meanwhile the effect of temperature was also discussed.This work could serve as a theoretical reference for the setup of the non-thermal plasma flue gas denitrification stage and applying the ammonia reagent.