SiGe-OI (Silicon Germanium on insulator) material is a new type of semiconductor material, and the refractive index of waveguide region can be effectively improved in electro-optic modulator with SiGe-OI materials. More importantly, used SiGe-OI material, the injection efficiency of electro-optic modulator can be improved. Based on the early research of SiGe-OI optical waveguide, PIN structure is selected as electrical modulation structure of electro-optic modulator, and the electrical modulation mechanism of PIN structure is studied. PIN structure is built by ISE-TCAD soft, and the carriers injection efficiency are analyzed. The doping concentration of active region, the width of active region, the width between active region and waveguide, Ge content and the other parameters are analyzed and optimized. Finally, compared with SOI electro-optic modulator, the carriers injection efficiency of SiGe-OI electro-optic modulator are increased 87.5%, in other words，modulation voltage of SiGe-OI electro-optic modulator can be reduced, so as to effectively reduce modulation power.