Abstract: A new kind of polarization-independent and temperature-insensitive electro-optical modulator is presented by the aid of the relationship between the electro-optical coefficients of LiNbO3 crystal. The modulator is comprised of two pieces of LiNbO3 crystals, and a pair of collimators. The light propagation in the modulator is studied with the wave coupling theory of linear electro-optic effect. It demonstrates that the modulated output intensity doesnt depend on the polarization of incident light. Furthermore, it shows that the disturbance of the output intensity is less than 1.5% as the temperature variation is -20℃～60℃, and dI0/dT is better than 0.0002, which means that the modulator has a wonderful thermal stability.