Abstract: Slope gradient is one of indispensable internal factor during the development process of landslides. After counting and analyzing a great deal of gradients at 113 soil landslides in Goupitan reservoir area, we find that the distribution of gradients have the characteristics of the normal distribution. Using Chi-square test, we verify the gradients of landslides follow normal distribution and establish the function that reflect the relationship between gradient and probability of soil landslides. According to the relationship, we calculate the probability of landslide in different gradient ranges. We then divide the probability into three kinds. The gradients of 25.0～45.0have the maximum probability to soil landslides, which accounts for 60.47% of the total landslides. The gradients of 18.0～25.0and 45.0～51.0have the middle probability to soil landslides, which accounts for 25.46%.The gradients less than 18.0or more than 51.0have the minimum probability to soil landslides, which accounts for 14.07%.The research result inosculates preferably with the fact. The result of this paper not only provides potent gist to the construction of Goupitan reservoir area in future, but also provides a new idea to determine the weighting and index quantification in the process of assessment the landslide danger degree.