The invention discloses an adsorbing fixed-type synchronous rotating auxiliary device for sewing round cut pieces. The auxiliary device comprises a control system, a transmission system and an adsorbing system. The control system is connected with the transmission system, the adsorbing system and a drive system of a sewing machine through a PLC. The transmission system comprises a stepping motor, a gear I, a gear II, a hollow shaft, a bearing, a bearing pedestal, a disc I and a disc II, wherein the gear I and the gear II are connected with the stepping motor, the hollow shaft penetrates through the center of the gear II, the bearing and the bearing pedestal are arranged in the middle of the hollow shaft and are parallel to the stepping motor, and the disc I and the disc II are arranged at the top of the hollow shaft. The round cut pieces manufactured by means of assistance of the auxiliary device are good in sewing quality, efficiency is high, two locating working procedures can be omitted, the total benefits can be increased by ten times or more, product uniformity can be ensured by operation of different personnel, and dependency on the technology of operators is reduced.