Abstract: Fractal dimension method is one of the effective methods to quantify the valley differences. However, there are differences in the upstream, middle and downstream of the valley. How the valley level affects the box dimension of the valley remains to be explored. Based on 1∶10 000 DEM data source, the global and segmented box dimensions of Suide small valley in the Loess Plateau of Northern Shaanxi Province were studied, and the global and segmented box dimensions of the primary tributary were compared and analyzed. The results showed that: in small watershed, the box dimensions of different confluence thresholds fluctuated in a certain range with different thresholds, the box dimensions of 200 and 1 800 thresholds were 1.48 and 1.23, respectively; the box dimensions of the upper reaches of small watershed were 1.07 and 1.02, respectively, which corresponded to the early stage of valley development; the box dimensions of the middle and lower reaches increased, which were all 1.66, which corresponded to the peak age of valley. The global box dimension of the first tributary was lower than that of the whole watershed, which was 1.29 and 1.08 respectively. The box dimension of the first tributary located in the upper reaches of the watershed was the smallest, which was 0.87 and 0.94 respectively. The results showed that the box dimension method could reveal the differences of gully morphology to a certain extent.