La3Ga5SiO14 crystal (LGS crystal) is an optical nonlinear material with high damage threshold, high electro-optical coefficient and excellent electro-optical performance. LGS crystal belongs to trigonal system structure, smaller thermal expansion coefficient, thermal expansion anisotropy of crystal is weak, the temperature of the high temperature stability is good (better than SiO2), with two independent electro - optical coefficients are as good as those of BBO Crystals.