The structure and the principle for the polymer electro-optic microring resonator (MRR) switch are proposed as well as the transfer functions. The structural parameters are optimized; the transmission characteristics are analyzed including the output power, switching time, switching voltage, insertion loss, and crosstalk. When the operation voltage is 0V, the insertion loss and crosstalk are ∼1.2 and −20.2dB, respectively; when the operation voltage is 10.0V, those are ∼0.35 and −20.0dB, respectively. Furthermore, a novel method is presented for analyzing time-domain response of the device and the switching time is determined to be ∼10.71ps. These results indicate the favorable switching functions of the designed device.