Cold flow field of a typical low nitrogen oxides (NOx) swirl burner were studied by numerical simulation bases on solving three-dimensional (3d) Reynolds average steady Navier-Stocks equations with realizable k-epsiv turbulent model which can reflect strongly swirling flow fields more accurately than the standard k-epsiv model. Different air distribution modes are chosen to be the boundary conditions which are similar to the model test modes and it proved the correctness of the mathematical model by contrasting with the measured data of the test on the model of the burner. The results of the simulation indicated that when the other air velocity magnitude is the same, the different central air has a great effect on the formation of the recirculation zone near the outlet of the burner; the effect of the internal secondary air on the recirculation zone took the second place; the effect of the outer secondary air on the formation of the recirculation zone were not obvious. When the air velocity magnitude is all the same, the different internal secondary air blade position can influence the swirl strength which is very effective on the formation of the recirculation zone.