Abstract: In order to study the influence of slope gradient, slope position and other topographic factors on the change of soil carbon and nitrogen, the change characteristics of soil organic carbon, total nitrogen content and carbon nitrogen ratio of different layers (0-20 cm, 20-40 cm) under the slope gradient, slope position and their interaction were studied. The results showed that: (1) the content of soil organic carbon and total nitrogen were generally low, and their coefficients of variation were 0-20 cm > 20-40 cm, while the CV% of carbon nitrogen ratio was 20-40 cm > 0-20 cm; (2) with the increase of slope gradient, the content of soil organic carbon, total nitrogen and the ratio of carbon to nitrogen decreased gradually, among which the difference between 0° - 5° and 5° - 20° was significant; compared with 0° - 5°, the decrease of soil organic carbon and total nitrogen in other slopes was 10.07% - 28.69% and 3.72% - 23.74% respectively; (3) with the decline of slope position, the content of soil organic carbon and total nitrogen increased. Compared with the uphill slope position, the increase of soil organic carbon and total nitrogen were 6.48% - 15.98% and 13.43% - 30.34% in the middle and downhill slope position. The C/N ratio decreased with the decrease of slope, but the difference was not significant;(4) the slope mainly affects the change of organic carbon content, while slope position has obvious influence on the change of total nitrogen and carbon nitrogen ratio, especially the slope position interaction. In general, with the increase of slope gradient, organic carbon decreased significantly. The higher the slope position was, the more significant the decrease of soil total nitrogen was, and the more significant the increase of soil C/N ratio was, especially the coordination of carbon and nitrogen changes in the uphill and middle slope position of 20-40 cm soil layer was poor, and the C/N ratio increased significantly with the increase of slope position.