Abstract: In this paper，we present an approach to estimate the valley fractal dimension value based onDEM data. The flow accumulation is selected as scale and the scale-free range is selected based on thevalley shape self-similarity analysis. Within scale-free range，the length fractal dimension of valleyline is calculated by the linear fitting of the threshold value and the valley length，the structurefractaldimension is calculated by the average fractal dimension of multi-scale drainage networks. Experimen-tal studies show that the approach of estimating the valley fractal dimension value proposed in this pa-per can better meet the morphological structure of basin water.