Abstract: Aiming at the requirements of quantifying the changes of seepage field dammed by underground structures,the formula of the flow quantity and ground water level distribution of each part(upstream part,dammed part and downstream part) are discussed under the steady state after the seepage field has been dammed.An analytical method for groundwater flow field in a confined aquifer and a semi-analytical method for groundwater flow field in an unconfined aquifer are deduced respectively,after they have been up-dammed and down-dammed.Some numerical tests are conducted in order to illustrate the damming effect.The results indicate that the semi-analytical method for groundwater flow field can be approximated by the analytical method for the confined aquifer when the natural hydraulic gradient before damming is small.