A push-pull high-speed silicon-organic hybird Mach-Zahnder interference electro-optic modulator was designed based on silicon on insulator. By using beam propagation method, the structure of 3 dB beam splitter/beam combiner on the silicon on insulator (top silicon thickness is 220 nm) has been simulated optimally whose insertion loss is 0.106 dB. Mode converter was designed between stripe waveguide and slot waveguide to realize an efficient transformation of optical transmission mode, and the coupling efficiency is as high as 98.8% . Also, the influence of doping concentration of slot waveguide slab area on optical loss of slot waveguide was analyzed by using finite-difference time domain method when the doping concentration is 7×1017/cm3, the optical loss is nearly zero. The total loss of the modulator is 0.493 dB. Considering the effect of slot waveguide equivalent capacitance and slab area equivalent resistance on the bandwidths, the waveguide structure was simulated by film mode matching solver and the optical field confinement factor can be optimized to 0.199. The ultrafast pockels effect was exploited by using the silicon-organic hybird platform, which combines highly nonlinear organic materials with slot waveguides, and realizes a voltage-length of 1.544 V·mm and a bandwidth of 137 GHz.