To explore the influence of secondary air oxygen enrichment on flame shape, temperature distribution, radiation, NOx concentration and other parameters of rotary kiln, the feasibility of secondary air oxygen enrichment was studied. The numerical simulation of oxygen enriched combustion in secondary air were carried out for a rotary kiln under actual working conditions by using ANSYS Fluent 15.0 software. For the gas phase, the RNG k-ε model was used to simulate the turbulent flow. For the particle phase (pulverized coal), the discrete phase model and discrete random walk model were used to calculate the trajectory of the particle phase. For the pulverized coal combustion process, the species transport model combined with the Finite-Rate/Eddy-Dissipation model was used, and radiation was expressed with the P-1 radiation model. The pollutant model was used to calculate the generation of NOx in the rotary kiln, considering the generation of thermal NOx and fuel NOx in the rotary kiln, and NOx reduction by reburning. The results showed that after the secondary air was enriched with oxygen, the gas flow fields near the burner did not change significantly, the covering shape of the high temperature area did not change obviously, and it was still in the shape of "mallet". At the front end of the rotary kiln, the combustion speed of pulverized coal volatile and char was accelerated, the overall temperature increased, the maximum temperature was increased from 2386 K to 2427 K, and the radiation received by the wall surafce was also increased. However, the generation of NOx had also increased significantly. According to the calculation, the mass concentration of NOx at the outlet increased from 247 mg/m3 to 367 mg/m3. Considering the cost of oxygen production and NOx emission, the overall effect of oxygen enriched combustion in secondary air was not ideal.