A cross bus single microring electro-optical switch model is proposed based on the theory of coupling modes, electro-optical modulation, and transfer matrix. Simulation is carried out for the 1561 nm wavelength light signal. Result shows that the switch voltage is about 400 V, the interrupt is less than -30 dB and the insertion loss is less than 4 dB. The response time is only 5.4 ps, in which the rise and fall time on the microring is only 0.32 ps. Besides, since the electro-optical switch is controlled by a single-pole double-throw switch, the three states of the latter can be realized through adding driving voltage on microring and U bend waveguide. Unlike the tranditional microring switch, the above-mentioned one not only can realize the selection of light signal pathway, but also can let the two output ports have light signal sent out.