[Objective] Landslide occurrence probability was calculated and verificated using three-dimensional model to provide a new way for quantitative evaluation of landslide stability.[Methods] Rosenblueth method was used to calculate the probability of three-dimensional landslide by FLAC 3D numerical simulation software. Its result was compared with the one calculated by two-dimensional probability model.[Results] Taking a slope in the three gorges reservoir area as an example, we calculated the landslide probability under two kinds of working condition using two and three dimensional models. According to the result form the three dimensional model, the probability were 13.57% and 21.77%, respectively, both belonging to low risk level. These probabilities were thought to be the actual situation. However, the calculated probabilities from two-dimensional model were as high as medium risk level.[Conclusion] Rosenblueth method performed more reliable than two-dimensional probability evaluation models do in evaluating landslide stability.