Abstract: Based on the mathematical model of the seepage in jet grouting,the paper inferred the pressure distributed formula in the district with the cement liquid injection and the raw water area, and the decline pressure in well bottom after stopping injection cement liquid. The pressure in well bottom relation with grouting time, the viscosity of cement liquid and the permeability in the confined aquifer were analyzed. The empirical formula of the grouting pressure with ratio of the water cement was established. The results are used in the engineering, and a good fulfilment is obtained.