A compact polarization beam splitter (PBS) based on a microring resonator is proposed and demonstrated numerically by utilizing the full vectorial mode-matching (FVMM) theory and the coupled mode theory (CMT), which are introduced in the aspects of the width of waveguide, the height of waveguide, the radius of microring, and coupling coefficient, etc. Simultaneously, the finite difference time-domain (FDTD) method, a powerful and accurate method for finite size structure, is chosen to simulate and design this PBS. When TE and TM polarized light at 1.55μm are launched into the input port simultaneously, the resonator will drop TM polarized light to the drop port and transmit TE polarized light to the through port. In this way, two orthogonal polarization states are split and transferred to different output ports. The extinction ratio in the order of 10dB is achieved initially based on our recent work. The initial experimental results are also given, which includes three microring resonator with the radius of 15μm, 10μm, and 5μm, respectively. The proposed PBS structure could be utilized to develop ultracompact optical polarization modulating device for large-scale photonic integration and optical information processing.