An open ratio adjusting device for a cutter head of a shield tunneling machine comprises a five-connection cutter holder, a six-connection cutter holder and face plates, wherein the five-connection cutter holder and the six-connection cutter holder are arranged on the cutter head and arranged in the vertical direction and the horizontal direction respectively, and the face plates are arranged at diagonal positions. The cutter head is provided with cross beams concentric with the cutter head, notches are formed between each cross beam and the five-connection cutter holder, between each cross beam and the six-connection cutter holder, between each cross beam and the corresponding face plate and between every two adjacent cross beams, and cover plates are correspondingly arranged outside the notches and movably connected with the notches. The device is low in cost, simple in structure, high in safety and installation speed in the high-pressure bin entry construction process and capable of effectively achieving the adjustment purpose of the open ratio of the cutter head of the shield tunneling machine in stratums with sandy gravel of different particle sizes, effectively solving the problem of poor applicability of the open ratio of the cutter head, and solving the problem of personal risk of people for high-pressure bin entry steel plate welding.