Direct and accurate calculation on three-dimension watershed geomorphology is one of key issues in current fractal geomorphology.Based on the Fundamental principle of variational method

the three-dimension surface fractal dimensions of a indoor small watershed model were calculated.And based on DEM data of the watershed model under different development periods as well ad the function of windows analysis in ArcGIS 9.2

the three-dimension geomorphology minkowski dimension of the watershed model under different development periods were calculated and studied.The results indicated that: the organic combination of variational method and GIS makes it possible to calculate directly the three-dimension geomorphology fractal dimension

and the three-dimension geomorphology of the small watershed model under different development periods possess good fractal characteristics in non-scale range respectively.In addition

three-dimension geomorphology minkowski dimension not only indicates effectively the variations of the geomorphology of the indoor watershed model under different development periods

but also reflects accurately the dynamic characteristics of watershed geomorphology

as a result

it is feasible to make three-dimension geomorphology minkowski dimension as a quantitative index of the three-dimension geomorphology fractal character of the small watershed model.