Abstract: In order to compare the modification effect of the surface active agent and the chemical modifier on water glass, the surfactant sodium dodecyl sulfate and the chemical modifier polyacrylamide were used to modify the water glass. The experimental results show that the viscosity of the water glass decreases with the addition of the surfactant and the chemical modifier. The compressive strength of water glass sand was the highest when the added amount of surfactant was 0.6% (mass fraction), and the modification effect of surface active agent is better compared with that of chemical modifier. When the addedamount of modified water glass is 4% (mass fraction), the improvement on collapsibility strength of water glass sand resulted from sodium dodecyl sulfate is better than that from polyacrylamide when the blowing time is short, and that from polyacrylamide is better than that from sodium dodecyl sulfate when the blowing time islong.