The influence of inner diameter of hollow cylindrical permanent magnet on the levitation force of single domain GdBCO bulk superconductor is investigated by measuring the levitation force between the hollow cylindrical permanent magnet and the single domain GdBCO bulk superconductor. The results show that the levitation force is closely related to the inner diameter of the hollow cylindrical permanent magnet when the inner diameter (d) increases from 0 mm to 26 mm (minimum measuring gap distance Z=2 mm), and all the superconducting magnetic levitation force curve shows magnetic hysteresis phenomenon. With the increase of the inner diameter of the hollow cylindrical permanent magnet, the levitation force at a minimum distance decreases gradually from 14.8 N at d=0 mm to -0.1 N at d=26 mm. The levitation force at the minimum gap distance is negative when d ≥ 20 mm. When 0 mm ≤ dd ≥ 5 mm. The larger magnetic field strength of the superconductor can be obtained, and the levitation force can be effectively improved by the scientific and reasonable designing of the permanent magnet structure. The results have certain guiding significance for designing and optimizing the magnetic suspension bearing system, ring track and superconductor.