The invention discloses a middle sealing mechanism for cylindrical forming of a non-woven fabric. The middle sealing mechanism is characterized by comprising a feeding table, a feeding guide wheel, a middle sealing table, an ultrasonic scalding and welding device and a discharging guide wheel, wherein the feeding table and the middle sealing table are arranged in tandem in the feeding direction; the feeding guide wheel is arranged above the feeding table in a rolling manner; the ultrasonic scalding and welding device is arranged above the middle sealing table; the middle sealing table is an independent element and comprises a die frame, a left supporting plate, a right supporting plate and a scalding and welding bottom wheel; the left and the right supporting plates are connected with the left and the right sides of the die frame; the distance between the left and the right supporting plates is adjustable; the left and the right supporting plates are used for propping a passing non-woven fabric cylindrical model open; the propping size is the cylindrical forming size of the non-woven fabric; and the scalding and welding bottom wheel is arranged in the middle of the die frame in a rolling manner and is arranged over against a scalding and welding head of the ultrasonic scalding and welding device. The middle sealing mechanism solves the technical difficult forming problems in single-side middle sealing for cylindrical forming of thin type non-woven fabrics and can be used for production of non-woven fabric decontamination funnel anti-clogging bags.