The Digital Elevation Drainage Network Model (DEDNM) of the Shiguanhe River catchment is made from digital elevation model by Martz and Garbrecht method with spatial basin heterogeneity considered. Subwatershed, drainage network, and their spatial topological relations are generated automatically by computer. Then, spatial cumulative distribution probability of topographical index ln (a/tgβ)_i in the TOPMODEL is calculated. Therefore the parabolic exponent of soil tension water storage capacity distribution within each subwatershed in the Xin'anjiang model can be obtained by dimensionless processing with respect to cumulative distribution curve of ln(a/tgβ)_i . That makes the parabolic exponent in the Xin'anjiang model be physically based. Finally, the digital hydrological model is established. The case study on the Shiguanhe River catchment in the Huaihe River Basin, i.e., the intensified observation field of GEWEX Asian Monsoon Experiment Project, showed that the digital model performs very well not only in simulating runoff processes at any specific outlet, but also in simulating spatial distribution and temporal variation of hydrological elements and state variables (especially soil moisture), if compared with traditional hydrological models. That provides solid foundation for making full use of present observation information and thorough tapping potentials of hydrological data.