We proposed and theoretically discussed a polarization switch based on a multiple quantum well (MQW) microring resonator (MRR) with an L-shaped waveguide as a dynamic polarization control device. The L-shaped waveguide was useful to obtain the rotation angle of the principal axis of 45° even when the core layer has form birefringence such as an MQW. The MRR functions as both a polarization converter and a wavelength filter. As an MQW core layer, a multiple five-layer asymmetric coupled quantum well (FACQW) was assumed. Polarization switching of an inputted light with a selected wavelength was successfully demonstrated at an operation voltage as low as 0.2 V using the electrorefractive index change in the MRR waveguide. The maximum polarization extinction ratio was more than 35 dB. The high-speed and low-voltage polarization switching can be realized with the proposed MRR polarization switch.