The invention relates to the technical field of machining equipment, in particular to a sealing technology for preventing air leakage at a kiln tail of a rotary kiln. The rotary kiln comprises a kilncylinder body; one end part of the kiln cylinder body is provided with an opening; the opening of the kiln cylinder body is connected with a flue gas chamber; an external housing is installed at the outer walls of the kiln cylinder body and the flue gas chamber; a material retaining plate is arranged at one side of an air spraying and blowing chamber; a first spraying and blowing pipe is installedat one side, far away from the material retaining plate, of the air spraying and blowing chamber; a first friction ring is installed at one side part of a sealed bin; an adjusting bolt is installed at the bottom of the first friction ring; a stainless steel flap is movably installed on the first friction ring and is connected with the outer wall of the sealed bin; and the first friction ring is movably connected with the top of the kiln cylinder body through the adjusting bolt. The sealing technology provided by the invention solves the influences of air leakage and material leakage on environment, can effectively reduce production power consumption and coal consumption and can prolong the replacement period of a friction part; the replacement period of the friction part is prolonged to 3years or longer if a discharging system at the kiln tail is free of damages, and a process for manually clearing accumulated dust is not needed, so the labor intensity of a worker is alleviated, andpotential safety hazards are eliminated.