This paper investigates the influence of rainfall on the activity of the Kutlugun landslide by examining relationship between rainfall and three-dimensional (3D) displacements. By analyzing periodically observed 3D GPS data, a dynamic analysis method based on the Kalman filter solution was developed to quantitatively assess the effect of rainfall on this landslide. The mathematical and statistical structure of the dynamic model regarding intensive rainfall was also described, including computations of 3D displacements and the parameter that shows the geometric reflection of rainfall effect on point movements. Defining and calculating causative relationship analyzed that between the rainfall and rainfall-induced 3D displacements of landslides. Finally, acceleration effects of intensive rainfall on the Kutlugen landslide were investigated. Results indicated that rainfall-induced 3D displacements of Kutlugun landslide show good correlation with the effective rainfall.