Abstract: There are numerous curved slopes adjacent to mountainous terrain. Their failures have significant three-dimensional (3D) characteristics. The raditional analyses of slope stability are based on two-dimensional plane-strain conditions and cannot involve the 3D effects. In this study, 3D stability analysis of curved slopes is carried out based on the limit equilibrium method of variational theory. The pseudo-static method is used to assess the 3D stability of the curved slopes subjected to the earthquakes. The critical slip surfaces are also determined by the optimization procedure. The results are compared with those calculated by other methods, indicating that the proposed method can obtain more critical solutions on the 3D stability of curved slopes. The geometrical parameters of the slopes (e.g., curving angle, curving radius, slope angle) and the horizontal seismic acceleration coefficients are considered to investigate the influences of the 3D effects on the slope stability. The results demonstrate that the 3D effects can be completely provided for a slope with a small curving angle to increase the safety of the slope, and reducing the curving radius can significantly enhance the 3D effects and enlarge the depth of the critical slip surface, whereas it is not pronounced for the slopes with large angles and horizontal seismic acceleration. In this situation, the traditional plane strain analysis can be adopted neglecting the 3D effects.