The effect of heat treatment on transmittance and thermal expansion of low expansion transparent glass ceramic with Li2O, Al2O3 and SiO2 as its main components was investigated by using DSC, XRD, dilatometer and spectrophotometer, etc. The proper heat treatment was determined. The glass ceramic with high transmittance of 76.58% and near zero expansion coefficient was nucleated at 720 ℃ for 10 h and crystallized at 880 ℃ for 1.5 h. Its main crystalline phase is β-quartz.