Abstract: This research presents a technique of an electro optic effect and electro-refractive which considered as one of the important techniques in the optical communication systems. In this study, a method is introduced to solve the problem of large length of 2×2 MZI electro-optical switch forlithium tantalate LiTaO . By using 3 mathematical model for designing MZI electro-optical switch by analyzing the effect of external electrical field on the refractive index with better electro-optical coefficient and refractive index. Finally, in this research, the researchers achieved better performance with low driving electrical field, small size of switch and wide band using near infrared wavelength.