Abstract: To acquire the effective of additive amount on the liner thermal expansion of gypsum mixture, the water addition, the submicron silicon dioxide addition and the silica sol addition were inspected through single-factor and orthogonal experiment, and the microstructure of submicron silicon dioxide-gypsum mold was observed by SEM.The results show that the fire shrinkages of the better gypsum mold is 1.505% minus, when the water / powder ratio, the submicron silicon dioxide addition and the silica sol addition are 52%, 4%, 3% respectively; The over-all structure of the gypsum mold is interlaced by the silica sol and network structure.