The invention discloses a composite sealing device for a centrifugal machine bearing. The composite sealing device comprises a transmission cover (2), an outer bearing cover (3), a bearing seat (4), a bearing (5), an inner bearing cover (6), a sealing bracket (7) and a sealing gland (8) which are sequentially sleeved outside a centrifuge drum spindle (1); and a sealing element (9) is arranged between the sealing bracket (7) and the drum spindle (1), an airtight sealing passage (7.1) is arranged on the sealing bracket (7), the inner end of the airtight sealing passage (7.1) is pressed close to the outer surface of the drum spindle (1) and is located between the sealing element (9) and the sealing gland (8), and the outer end of the airtight sealing passage (7.1) is connected with a high-pressure air source (10). The composite sealing device provided by the invention can effectively prevent such harmful substances as ultra-fine hard powder, corrosive gas and the like from entering the bearing, and belongs to the technical field of the sealing device.