Abstract: For the development of fine electro-optic deflectors, an equivalent expression of refractive index gradient in a deflector of cascade crystal prisms was analyzed under the condition of paraxial approximation. Equations of the deflection angle and ray trajectory of an electro-optic deflector with different geometric constructions were summarized and their deflection characteristics were studied by means of numerical analysis. Deflection sensitivities of trapezoidal, horn and parabola shaped deflectors were compared with each other. It is helpful for the design of electro-optic scanners with big deflection angles.