By taking 5m grid cell DEMs as an experiment basis, the relation between flow accumulation threshold and gully density in the Loess Plateau area, Northern Shaanxi, China, is invest igated quant itat ively and stat ist ica-lly. Experimental results show that a stat istical model could be constructed as a formula. In the formula, the coef f-icient is found to have a strong relat ion w ith terrain complexity and types and play a signif icant role in the model. In the fixed terrain area, a reasonable flow accumulat ion threshold could be derived based on the model, which is of critical significance not only in the theory, but also in application.