Abstract: At present, the two-dimensional profile is widely used for slope stability analysis, which can efficiently and accurately evaluate the stability of the slope. However, the two-dimensional section cannot describe the three-dimensional spatial shape and three-dimensional sliding body of the most dangerous sliding surface of the slope. In order to solve this problem, based on the stability analysis of the two-dimensional section slope, the three-dimensional most dangerous sliding surface of the slope is fitted by using the spline function by associating multiple sections with the three-dimensional slope model. Firstly, the relationship between the two-dimensional profile and the three-dimensional slope space is established by setting the profile name, horizontal coordinate positioning and elevation positioning of the graphic elements in the profile line and the two-dimensional profile. Secondly, the most dangerous sliding surface lines of each section are automatically generated, and the most dangerous sliding surface lines of each two-dimensional section are converted to three-dimensional slope space by using the coordinate transformation formula. Finally, the spline function interpolation is used to fit the most dangerous slip surface lines in the three-dimensional space to construct the three-dimensional most dangerous slip surface. Taking the southwest slope of an open-pit mine in Xilinhot, Inner Mongolia as an example, a three-dimensional engineering geological model of the slope is established, and five two-dimensional profiles for slope stability analysis are generated. Through this method, the three-dimensional most dangerous sliding surface and three-dimensional sliding body of the slope are successfully generated.