The cement-sodium silicate slurry is widely used in grouting and water stopping, and the solidification characteristics of slurry have the direct effect on such engineering. The gelation time and fluidity of the slurry with different water/cement ratio have been studied on the theoretical basis of setting and hardening of cement-sodium silicate slurry. Contrast tests have been done to research the influence of admixtures to the solidification characteristics of slurry such as FDN, SM, NF, UNF-5, citric acid, polyphosphate, tartaric acid and disodium hydrogen phosphate. The retarding performance of disodium hydrogen phosphate is specially studied by means of the data of contrast tests, and the influence law of the disodium hydrogen phosphate to the solidification characteristis of cement-sodium silicate slurry has been got. The different formulas of cement-sodium silicate slurry are designed according to the initial setting time.