To manufacture high precision optical glass microstructures, finite element simulation and experiments of precision glass molding (PGM) are carried out to study the influence of relaxation effect on internal stress and deformation of the glass material. Two kinds of microstructures including microgrooves and micropyramids are fabricated by PGM. First, a two-dimensional axisymmetric finite element model of the PGM is established, and three kinds of molding schemes are put forward and analyzed, including quick molding and holding for a period of time, molding with low speed, molding by gravity. The advantages and disadvantages of the three schemes are also analyzed. Second, the microgrooves are fabricated using the scheme of molding by gravity, and then the existing problems are discussed. Finally, the micropyramids are fabricated by the low speed molding method, and the forming profiles are compared.