The change of the band gap and refractive index of SiO2 with strain is analyzed by using the first principles method, and the change of photoelastic coefficient with strain is further calculated. The results show that when the tensile strain along z axis increases, the band gap of SiO2 decreases. When the compressive strain along z axis increases, the band gap of SiO2 firstly increases and then decreases, reaching a maximum value when the compressive strain is 2%. When the refractive index changes from tensile strain to compressive strain, the refractive index increases gradually. Each component of the photoelastic coefficient has different trends with the change of strain. The results of this paper are helpful to the optimal design of related devices.