Combined sealing device

The utility model relates to a novel combined sealing device which is formed by that a gas spiral groove seal and a ferrofluid seal are combined, wherein, a moving ring of the gas spiral groove seal is arranged on a rotating shaft; spiral grooves are overspread on the surface of the excircle of the moving ring at equal intervals; a fixed ring of the spiral groove seal is fixed on a reducing sleeve which is connected with a base of a device to be sealed; a sealing gap is arranged between the moving ring and the fixed ring of the spiral groove seal. A ferrofluid seal portion in the sealing system is positioned between the spiral groove seal and a sealing pressure cavity; composed of a permanent magnet fixed on the surface of the inner circle of an outer sleeve, two magnetic boots and a moving ring of a ferrofluid seal; the ferrofluid is poured at the part of a gap between the magnetic boots and a lug boss of the moving ring.