Factor analysis is adopted to analyze the displacement monitoring data for a landslide in Three Gorges Reservoir area. The monitoring points are used as variables, and three common factors are extracted to characterize the original data. Meanwhile, the loading matrix of common factors is obtained. Furthermore, according to the distribution of factor loadings and the information reflected by the monitoring point variables, the practical meaning of each common factor is determined. It's indicated that reservoir water is the biggest influencing factor causing landslide deformation, followed by precipitation and the microtopography of monitoring points. The value of displacement induced by reservoir water is obtained by factor loading. According to the changing trend of cumulative displacement of monitoring points on the middle and front of the landslide profile, the landslide deformation mechanism under the influence of reservoir water is analyzed.