Abstract: Fractal dimension of natural water system,to some extents,could reflect geological structure and crustal movement behaviour in the areas.Whereas,a method of calculating fractal dimension is carried out by artificial now.In this paper,based on Visual-Basic programming,a computer processing and fractal dimension calculation of natural water system has been carried out by computer technique.As an example,the fractal dimensions of three water systems and their main channels in China (Yellow River,Yangzi River and Pearl River)are calculated by using this program.This computing method is fast,accurate and applicable to various lineaments.