In this study, the influence mechanism of crucible rotation rates on the flow field and oxygen concentration of 200 mm semiconductor-grade Czochralski monocrystalline silicon under transverse magnetic field was investigated using ANSYS finite element software. The results show that flow field and oxygen concentration distribution of the silicon melt exhibit three-dimensional asymmetry under transverse magnetic field. The convective forms of the melt mainly include Taylor-Proundman vertices, buoyance-thermocapillary vortices, and secondary vortices. The former two contributed to the volatilization of oxygen, while the latter one had a suppressing effect. When the crucible rotation rate is low (0.5~1.0 r/min), the weaker convective strength of the melt results in low thermal conductivity efficiency between the crucible wall and the solid-liquid interface, and oxygen mainly migrates to the solid-liquid interface through a diffusion mechanism, resulting in high oxygen concentration in silicon melt. When the crucible rotation rate is high (2~2.5 r/min), oxygen migrates to the solid-liquid interface through strong convective forms. As the crucible rotation rate increases, the strength of the secondary vortices and buoyancy-thermocapillary vortices increases, and the region affected by the latter moved away from the free surface, resulting in a trend of first decreasing and then increasing oxygen concentration in the silicon melt. Both the numerical simulation results and experimental results indicate that a crucible rotation rate of 1.5 r/min is optimal for obtaining monocrystalline silicon with lower average oxygen concentration. The results of comparative analysis between experiments and numerical simulations can provide a reference basis for optimizing the parameters of the crystal growth process under transverse magnetic field.