Abstract: The physically based hydrological models are based on the physical descriptions of water movement within the overland,river channel and soil,which makes it promising that the hydrological modeling depends less on the calibration of watershed responses while depends more on the observations and measurements of clmiate and landscape themselves.The spatial discre tization is the very first step in the development of physically based models,and at the same time,it is also the principle way to represent the spatial heterogeneity of landscape properties such as topogra phy,soil,vegetation,etc.The grid based method for spatiald iscretization is one of most commonly used ways for its smiplicity.However,the method cannot represent the heterogeneity in a realistic and efficient manner,and most importantly,the gird based models may not be suitable for the modeling of multiscale hydrological rocesses.In this study,a physically based hydrological model is developed on a triangu lated irregular network(TIN).The model partial different equations(PDEs) derived at micro scales include the Richards equation and Saint Venant equations.The model is resolved numerically using the finite volume method(FVM) that can integrate the PDEs over the controlling space into ordinary differential equations(ODEs).The use of FVM can ensure the balancing of watermass in the numerical solution,as well asmakes it easier when coupling to other ODEs of canopy interception and ground depression.The model is tested over the upper region of the Qin river basin.The results show the reasonable modeling accuracy and efficiency.