Abstract: For simulation of the hydrology in a watershed by distributed hydrological models, besides the meteorological and hydrological data needed, the detailed information such as topography and watershed networks is also necessary. Traditionally, the drainage networks were derived from digital elevation models (DEM) using commercial software, which is time consuming and inconvenient for operation in hydrological modeling. Based on a distributed hydrological model (DHM) developed by us, an automatic watershed information extraction module was developed which is able to be integrated into the DHM seamlessly using the same computer language of C#. Therefore, most of the data transferring can be finished in memory with no occupation on hard disks, so it is highly efficient when running. The algorithms for the watershed information extraction were introduced, such as the algorithms of removing of depression and flatten areas, generation of flow direction and accumulating flow direction, obtaining Strahler river order, dividing of sub watershed and calculation the sequence of flow order and water-drainage length. This system overcomes the limitations of using commercial software for extracting watershed information, and also favors the modeling system for convenience of modifying and extending the model easily in the future.