Abstract: The characteristics and hazards of magnesite calcining of kiln flue gas are discussed, along with principles and processes of the SCR denitrification method. Flow field of the SCR reactor was simulated by Fluent software using a standard turbulence model and a porous medium model. This SCR reactor is designed for high temperature factory kiln calcination of magnesite, and its design was further optimized by numerical simulation. Simulation results showed that installing a fluid regulator in the SCR reactor slightly improved flow field, and size of the fluid regulator lattice had little effect on the flow field. Simulation also revealed the optimum structure and location of guide plates, thereby providing excellent denitrification results.