The invention provides a shaft sealing body, a shaft sealing device and a control method. The shaft sealing body comprises a main sealing body and a sealing ring fabricated by a flexible material. The main sealing body is provided with a through hole allowing a shaft to penetrate through in the axial direction, and a preset gap is reserved between the through hole and the shaft; the sealing ring is connected to the position between the shaft and the main sealing body in a sleeved manner and arranged in the preset gap; the outer wall of the sealing ring is provided with first annular slots in the circumferential direction, the main sealing body is provided with pressurizing holes, one end of each pressurizing hole communicates with the corresponding annular slot, the other end of each pressurizing hole penetrates through the side wall of the main sealing body and is used for being connected with a pressure adjustment pump. Sealing is achieved through the sealing ring; due to the fact that the sealing ring can be deformed, the sealing device is suitable for shafts of different diameters, wherein the shaft diameters are slightly changeable, and the application range of the sealing device is broadened; and due to the fact that the sealing ring is made of the flexible material, friction wear of the shafts is greatly reduced, and the service lives of the shafts and the service life of the sealing ring are prolonged.