The characteristics of burning pulverized coal motion and the combustion process are investigated by numerical simulation to analyze the relations between the NO x formation and the gas flow and burning pulverized coal moving in a swirl pulverized coal burner. The depth of particle penetration into the IRZ L dav and the effective time of IRZ τ eav are obtained under three swirl numbers s=0.5, 1.03 and 1.2, respectively. The results show that the minimum outlet NO x emission appears at the maximum L dav and τ eav and the minimum outlet NO emission, the maximum L dav and the maximum τ eav occur at the same time (s=1.03). It is also found that, the diameter of pulverized coal first increases, but then decreases the particle residence time τ int in IRZ.