Flow-induced vibration power generation devices are suitable for low-velocity ocean currents and are a current focus of research. Compared to metal springs, oscillator systems supported by permanent magnetic levitation offer greater advantages in capturing ocean current energy. To investigate the influence of mass ratio on the vortex-induced vibration characteristics of a rigid cylindrical oscillator, this study developed a magnetically levitated oscillator model. The magnetic force-displacement curve of the permanent magnetic spring was obtained using COMSOL software, and the magnetic force-displacement function was fitted by the least squares method. Simulations of a single cylindrical oscillator were conducted in STAR-CCM+.The results indicate that when the mass ratio increases, both the vibration amplitude ratio and vibration frequency of the oscillator decrease. At a mass ratio of m* = 1.095 and flow velocity of U = 0.6 m/s, the amplitude ratio A* reached a maximum value of 0.93. At m* = 1.095 and flow velocity U = 1.0 m/s, the oscillator frequency f reached a maximum of 1.98 Hz. Under the five different mass ratios, the vortex shedding modes of the single cylindrical oscillator were primarily 2S and 2P, showing significant similarities.