Taiwan is located at the boundary of plates, so earthquakes occur frequently. Whenever a landslide induced by earthquake, it will cause adverse effects on traffic and economy, even threaten residents’lives. Therefore, the reasearch on the landslide displacement induced by earthquake can evaluate the damage and the impact scope of the collapse, which is meaningful for the advice and planning of the high-risk areas. In previous studies, there are two methods for calculating the displacement induced by earthquakes. One is the sliding block method, which has easy access to parameters and analyzes rapidly, and is often used to analyze the seismic b ehavior of slopes. The other is the numerical simulation. The critical failure surface of numerical analysis is used as the sliding surface, the strength of the interface is changed, and the sliding displacement of the sliding block is obtained after dynamic analysis. In this study, simplified homogeneous slope models were built by changing the cohesions, friction angles and slope angles, and the depth and weight of the log-spiral sliding block and the critical failure surface in numerical analysis were compared.through the analysis,we suggest the usable range is c/γH<0.037、tan⁡∅/tan⁡α:0.8~1.2. Then the residual strength of the sliding surface is used to input the two-dimensional sliding block method and the numerical simulation, and the displacement results are compared. When the interface strength is reduced the lower the value, the greater the difference between the displacement results of the two methods. It is speculated that the reason for the difference is that the sliding block method cannot consider the influence of block deformation and energy dissipation. Then, the failure surface and sliding displacement were analyzed by the large-scale shaking table slope test and two in-situ collapse cases, and the analysis results were compared and discussed with the test conditions and terrain profiles. Through the simulation and comparison of the large-scale shaking table test, it is found that the failure surface and the starting point of the sliding and the sliding displacement result of two methods are consistent with the physical test. In the field case simulation, the numerical analysis and the log- spiral failure surface obtained the same results of the cliff collapse distance and the profile before and after the Chi-Chi Earthquake When simulating the sliding displacement, the acceleration of crest was input and the residual strength was used to analyze. There is little difference between the horizontal displacement and the horizontal variation of the topography of the slope, so the log-spiral sliding block method and numerical analysis can be used to infer the position of the failure surface and calculate the sliding displacement.