In order to explore the model of chemical grout diffusion which is more consistent with reality, we conducted tests on the time-varying characteristics of viscosity of CW epoxy grout, and obtained that the relationship between viscosity and time at a given temperature accords with exponential function. Furthermore, according to the spherical diffusion theory and the cylindrical diffusion theory, we optimized the formulas of epoxy grout quantity and grout diffusion radius in terms of time-varying characteristics. The optimized formulas reveal that the grout is in negative acceleration motion in the process of infiltration; the maximum grout diffusion radius and maximum grout quantity are dependent on the product of the parameters of viscosity-time function when other parameters which don’t depend on grout itself remain constant. Through comparison of the product of function parameters of different epoxy slurries, we conclude that the grout of which viscosity grows more slowly has better penetration.