A numerical simulation method of drainage hole in three-dimensional seepage field in underground engineering is presented according to the theory of seepage flow. Drainage holes are implicit in model and their data are gained according to pre-process. The relative positions of drainage holes are judged and their impacts are simulated through modifying the penetrability conduction matrixes of elements perforated by the drainage holes. And then drainage substructure method and implicit composite element method are compared via an example. Finally

a three-dimensional finite element method calculation program compiled by ourselves is used to simulate the seepage field of an underground hydropower house. The calculation result shows that the new method introduced is feasible to simulate drainage holes.