Four design schemes of flow deflector in the gas flue of selective catalytic reduction (SCR) denitrification system are simulated based on Kε turbulence model and 2D model by Fluent. By analyzing the speed profile and pressure drop of the import and export, the effects of the flow deflector on the import and export speed profile, pressure drop, and energy dissipation are studied. It can be concluded that flow field distribution could be significantly improved by putting the flow deflector into the gas flue. Reasonable flow deflector design can not only make the flow field distribution uniform but also reduce the pressure drop and the energy dissipation. With the increase of flow deflector dimensions, the flow field distribution will be more uniform. The pressure drop and the energy dissipation will increase because of the increase of resistance caused by flow deflector. The research results are helpful for designing selective catalytic reduction denitrification system. 