An optical waveguide microring resonator for picosecond switching window generation is reported. The design and simulation are presented. The multiple-ring-cascaded structure is adopted to design the transmission characteristic curve of the microring resonator. Utilizing the nonlinearity of the transmission characteristic curve,a narrow switching window can be generated with a sine-wave electrical control signal to shift the refractive index of the material. The modulation characteristics and switching window are researched with coupling matrix formalism. The dependences of the width and extinction ratio of the switching window on the driving voltage are analyzed. Results show that the width,extinction ratio and the insertion loss of the switching window driven by 10 GHz electrical voltage are better than 10 ps,40 dB and 1 dB,respectively. The proposed picosecond switching window generation technology only requires electrical control signal instead of high-quality optical control pulse. It possesses a high operation speed with simple structure,low transmission loss,high extinction ratio and low operation voltage.