NOVELTY - Autotrophic denitrification of granular sludge, comprises inoculating flocculent into municipal domestic sewage, performing biological filtration back-washing, manually adding water, controlling ammonia nitrogen, nitrite-nitrogen, phosphate, calcium carbonate, pH, reacting at temperature of 28-32 degrees C to control ascending flow speed and dissolved oxygen, raising the initial flowing speed and initial hydraulic retention time (HRT), controlling initial settling time, and successfully starting process to control nitrogen nitrite accumulation.    USE - The method is useful for autotrophic denitrification of granular sludge (claimed).    ADVANTAGE - The method is capable of denitrifying granular sludge in a simple and rapid manner.    DETAILED DESCRIPTION - Autotrophic denitrification of granular sludge, comprises inoculating flocculent into municipal domestic sewage, performing biological filtration back-washing, where the sludge has a grain diameter of 100-150 nm and concentration of 2-3 g/l, manually adding water, adding and controlling concentration of ammonia nitrogen to 250-340 mg/l, nitrite-nitrogen to 0-8 mg/l, phosphate to 5-10 mg/l, calcium carbonate to 1400-2000 mg/l, pH to 7.5-8.3 under the condition of continuous aeration at first stage, reacting at temperature of 28-32 degrees C to control ascending flow speed and dissolved oxygen to 0.15-0.45 mg/l, rising the initial flowing speed to 93.59 cm/hour when the total nitrogen removing rate reaches more than 60% in 25-35 cm/hours for 3-4 hours, raising flowing speed to 280.77 cm/hour and initial hydraulic retention time (HRT) to 22 hours when the total nitrogen removing rate reaches 65-75% for 5-8 days, reducing HRT to 3-7 hours or 12 hours, controlling initial settling time to 15 minutes, reducing settling time to 3-6 minutes when the mud to the water outlet 5 cm at the time the next cycle, finally reducing settling time to 5 minutes, keeping idle for 2-10 hours, successfully starting the process when the mixed solution of grain diameter is more than 300 nm, and total nitrogen removal is more than 60%, and controlling nitrogen nitrite accumulation time to less than 8 mg/l.