The invention provides a sealing device for a positive pressure type pipeline. The sealing device comprises a cylinder body. The outer wall of the cylinder body is provided with two sets of sealing rings in the circumferential direction. Each set of sealing rings comprise at least two sealing rings. Each sealing ring is annular. The lower edge of each sealing ring is connected with the outer wall of the cylinder body. The upper edge of each sealing ring is suspended. The radius of a circle formed by the lower edge of each sealing ring in a surrounding mode is smaller than that of a circle formed by the upper edge of the sealing ring in a surrounding mode. The connecting surface between the upper edge and the lower edge of each sealing ring has a radian. The connecting surfaces between the upper edges and the lower edges of the two sets of sealing rings are opposite in opening directions. The two adjacent sealing rings in the at least two sealing rings of each set of sealing rings are arranged in a spaced mode. The upper edge of each sealing ring makes contact with the inner wall of the positive pressure type pipeline, the two adjacent sealing rings, the outer wall of the cylinder body and the inner wall of the positive pressure type pipeline form a sealed air chamber, and thus the sealing effect of the positive pressure type pipeline is improved. The problem that in the prior art, an O-shaped sealing ring is poor in pipeline sealing effect when positive pressure exists in the pipeline is solved.