The invention relates to a ladder type decompression de-foaming device for increasing the clear quality of molten glass. The device comprises a melting tank (1), wherein the melting tank (1) is connected with a decompression de-foaming tank (3) through an ascending pipe (2); a set of exhaust vents are formed in the decompression de-foaming tank (3); an outer shell (4) is arranged on the outer side of the decompression de-foaming tank (3); a vacuum pump (5) is connected with the outer shell (4); a heat-insulating material (6) is filled between the outer shell (4) and the melting tank (1); and the decompression de-foaming tank (3) is connected with a reflux tank (8) through a descending pipe (7). The invention has the advantages that the device is used for performing ladder type decompression on the molten glass; after the pressure is reduced, the foam diameters of the foams in the molten glass are gradually increased and the foams quickly overflow, so that the de-foaming and clearing effects are achieved; and compared with a traditional fixed target negative pressure method, the device can more fully separate air bubbles from the molten glass, the clear quality of the molten glass is increased, and the energy consumption is greatly lowered.