Abstract: With the rapid development of the infrastructure construction in southwestern mountainous areas in China. High-fill foundations of the Airport, Highways, Railways and other construction projects increase day by day. During the construction period, the large deformation of the fill area and long-term slow deformation of the post-construction stage directly affect the normal use of the construction site. Especially the fill works with the free faces of slope, slope and horizontal deformation of the filled soil are related to the overall stability of slope. This paper takes a high-fill slope in Anning city in Yunnan province as a case. The site survey and the monitoring data during the filling process was used in the deformation analysis. The numerical simulation software was used to study the deformation characteristics of the fill slope. The results show that the total deformation of the slope is dominated by subsidence, and the maximum occurs in the interior of the slope. Most of the deformation occurs during the construction. The settlement after construction is very small. The maximum vertical displacement of the slope occurs at the interface between the filling body and the original foundation soil. The contour of settlement is elliptical. The maximum of horizontal displacement of the slope occurs in the original soil. Horizontal displacement contour map is overall strip-like. It extends from the bottom to the earth of the slope. The horizontal displacement that changes greatly is consistent with the position of the actual surface crack. The research results have certain reference value and guiding significance to the construction process of the fill work with free face, the prediction and control of the deformation after construction and the study on crack disease on the upper part of slope.