Abstract: As a standard simulation procedure for curved lines and curved surfaces,the non-uniform rational B-spline has been widely used in the domain of computer-aided design.A three-dimensional sliding body was generated by using NURBS and the Janbu method based on the limit equilibrium was adopted to obtain the factor of safety for the given sliding body.The critical sliding body was found by using a new version of particle swarm optimization algorithm,in which the harmony search procedure was combined with the crucial search procedure using by PSO.A homogeneous soil slope and a complicated slope containing soft layer were analyzed using the proposed method and it was shown by comparative studies that the new method could be adopted in the three-dimensional slope stability analysis.