Blast furnace damping-down method without opening furnace top blow-off valve

The invention belongs to the technical field of blast furnace ironmaking operation, and particularly relates to a blast furnace damping-down method without opening a furnace top blow-off valve. During damping down of the blast furnace, feeding of the blast furnace is stopped, blast volume of the blast furnace is gradually reduced, gas pressure is reduced, and when the gas temperature is higher than 250 DEG C, furnace top water spraying cooling is started. When the gas temperature cannot be lower than 250 DEG C or the gas pressure is lower than 10 kpa through water spraying cooling, high-temperature gas is ignited and diffused through a high-temperature-resistant bag type filter, a gas diffusion valve and a gas diffusion pipe, a blast furnace air supply valve is closed, nitrogen is charged into the furnace top to maintain positive pressure, blast furnace damping down is completed, and the furnace top diffusion valve is kept closed; noise generated when gas is diffused from the furnace top and emission of dust