Abstract: A new model of drainage holes was proposed in order to accurately simulate behavior of the densely-distribute drainaged holes in seepage field with free surface,the difficulty of calculation due to the ill assortment of hole nodes with global net was avoided,and the hypothetical switch of seepage was intercalated in the overflowing holes in order to judge their function.The drainage hole nodes were treated as global net to avoid trouble and were considered as boundary nodes when the drainage holes were invalidated.By use of this method,the effect of each drainage hole could be well simulated and the problem of holes in seepage field with free surface was solved,meanwhile,and the numerical simulation of mass holes was very easy.The correctness and practicability of this method was proved by examples.