Numerical simulation was carried out on the High Temperature Air Combustion in an industrial furnace with a multi-jet burner. The effect of inlet oxygen concentration of the preheated air on the combustion characteristics was investigated. The standard k-e model was used to calculate the flow field and β function PDF was used to simulate the gas combustion. The radiation was simulated by a Discrete Ordinates method. NO was simulated by thermal NO model. The furnace was a rectangular chamber of 800 mm × 800 mm × 1400 mm. A circular fuel jet of a diameter of 10 mm is at the center of the wall. 5 circular air jets equably distributed around the fuel jet with different straddle angles. The results showed that inlet oxygen concentration of preheat air had a considerable influence on the local temperature, oxygen and NO distribution, resulting in a stable flame, an enlarged low-oxygen zone, an equable temperature distribution and a suppressed local high temperature, which led to the lower product of local NO. When the inlet oxygen concentration is 10%, the local NO concentration is lowered 2 factors than that under a 21% inlet oxygen concentration. The final NO emission is no more than 20 × 10-6 at an inlet oxygen concentration of 10%.