Combined with the spatial data processing capability of the Geographic Information Systems (GIS), the Pan Jiazheng method is extended from two-dimensional (2D) to three-dimensional (3D), and a 3D landslide surge height calculation method is proposed based on grid column units. First, the data related to the landslide are rasterized to form grid columns, and a force analysis model of 3D landslides is established. Combining the vertical strip method with Newton's laws of motion, dynamic equilibrium equations are established to solve the surge height. Moreover, a 3D landslide surge height calculation expansion module is developed in the GIS environment, and the results are compared with those of the 2D Pan Jiazheng method. Comparisons showed that the maximum surge height obtained by the proposed method is 24.6% larger than that based on the Pan Jiazheng method. Compared with the traditional 2D method, the 3D method proposed in this paper better represent the actual spatial state of the landslide and is more suitable for risk assessment.