Based on the problem to water load acted on the tunnel structure because of seepage after excavating, this paper uses the theoretical method on complex variable function to establish the seepage model considering the reinforced area, and the study obtains the seepage analytical solution considering the influences of the permeability and thickness parameters of reinforced area. One hand, the research indicates that the hydraulic gradient of the reinforced area will be amplified when the seepage capacity weakens; on the other hand, the hydraulic gradient is also amplified when the reinforced area is increased, but the effect of seepage capacity on the hydraulic gradient is more significant than the reinforced area. So the effect of the permeability of reinforced area on the seepage force in the surrounding ground is the main cause, and the effect of the thickness of reinforced area is much slighter. It can be seen that the thickness is just satisfied with the relative requirements. The compare between analytical solutions and numerical solutions proves that the analytical solutions are rational.