In order to overcome the disadvantage of Kemp-type photo-elastic modulator such as low modulation efficiency, processing technology difficulty, bulky et al., a photo-elastic modulation mode is proposed. Which uses LiNbO3 crystal piezoelectric properties to produce single crystal photo-elastic modulator. According to the theory of piezoelectric vibration and crystal optics principle, the crystal orientation dependence of physical properties is analyzed, and the relations of displacement and retardation amplitudes over voltage are derived. Then, the cutting-type and the optical path are optimized. The device is designed with dimensions 41 mm×7.7 mm× 17.1 mm in x-, y- and z-direction, 0° cutting angle (x-cut), z-axis for the optical path and electrodes on the xz-surfaces offer basic modulation frequencies at 73.71 kHz corresponding to the longitudinal oscillations in x-direction. Finally, the corresponding experimental equipment is built for the experimental verification; the result shows that: the voltage amplitude to achieve a half-wave retardation amplitude is only about 1.6 V for 633 nm wavelength, and the modulation voltage reduces about 4 times, compared with the LiTaO3 signal-crystal photo-elastic modulator whose cutting-type isn′t optimized.