Abstract: The study of the distributed hydrological model is a hotspot in recent years.Because some problems in the fully distributed hydrological model cannot be settled now,an alternative conceptual distributed hydrological model is put forward. An important problem in the conceptual distributed hydrological model is how to determine the storage capacity on every grid. Considering the similarity between the maximum of grid soil moisture deficiency and the grid topographic index,a logarithmic Weibull function relation existing between them is discovered.And then a method for calculating the grid storage capacity with the grid topographic index is put forward.The method is applied to the grid distributed hydrological model with incompact structure.The results shown that,in the ungauged basin,we can get some hydrologic parameters from geographic parameters and find a new approach.