The invention discloses a seal cover device. The seal cover device is connected with a discharge device and a seal tank. The end face of the inlet end of the seal tank is provided with a groove. The seal cover device comprises an inner casing, an outer casing and a drive assembly. The first end of the inner casing is suitable for being connected with a discharge outlet of the discharge device. The first end of the outer casing is arranged on the inner casing movably in a sleeving mode, and the second end of the outer casing extends out of the inner casing. A flexible seal part is arranged between the peripheral walls of the outer casing and the inner casing so as to preventing air from entering the space between the outer casing and the inner casing through the first end of the outer casing. The outer casing is fixed to a seal pipe on the peripheral wall of the outer casing. The end, extending out of the outer casing, of the seal pipe is suitable for extending into the groove. The drive assembly is connected with the outer casing/or the seal pipe so as to drive the outer casing to move. According to the seal cover device, moving space is increased, the structure is simple, a seal tank can be replaced conveniently, industrialized production can be achieved, meanwhile, leakproofness of the seal cover device is improved, and air is isolated effectively.