The invention relates to a spherical cap type inspection window seal ring replacing device and a replacing method. The replacing device includes a
flange, a window seat is mounted on the
flange through a plurality of O-shaped rings, a spherical cap type inspection window is mounted on the window seat, a compressing ring is mounted on the circumferential surface of the joint of the spherical cap type window and the window seat through a compressing ring rubber
blanket and a sealing device, and meanwhile, the compressing ring and the window seat are locked through an inside hexagonal bolt; and aplurality of replacing tools are further mounted in the circumferential direction of the window seat at intervals, the replacing tools includes a supporting seat, the rear end of the supporting seatextends upwards to form a right-angle frame, a through hole is formed in one of the right-angle sides of the right-angle frame, a long bolt is mounted on the through hole, thus the through hole is connected with the window seat and the
flange, locking is conducted through a first nut, the bottom of the front end of the supporting seat extends downwards to form a mounting sleeve, the mounting sleeve is internally loaded with a lead screw and is fixed through a second nut, a pressing plate is fixed to the bottom of the lead screw, and the bottom surface of the pressing plate abuts against the spherical cap type inspection window through a tool rubber
blanket. Work is reliable, and dismounting is convenient.