The flame temperature is higher and thermal NOx generation is bigger when flat flame combustion and the regenerative combustion technology are used together. Flue gas recirculation is one of the effective ways to reduce thermal NOx generation in the process of HTAC. Flame features, furnace top temperature distribution and generating characteristic of NO with and without flue gas recirculation are studied by means of flat flame gas stove of HTAC and analytical instruments for flue gas and thermocouple. The results show that flue gas recirculation make dark area of flat flame smaller, burning area expand, flame temperature distribution more uniform and NO concentration in flue gas obviously decrease. Peak temperature decreases 9 ℃，valley value of temperature increases 37 ℃, and the maximum NO concentration reduces 20%.