A new procedure is presented to generate kinematically acceptable slip surface of general shape.The modified

i.e.

discontinuous flying particle swarm optimization algorithm（DFPSO） is proposed to avoid the severe time consuming occurred in the original particle swarm optimization algorithm.Spencer’s method of slices is adopted to calculate the factor of safety of given slip surface.Several example slopes with complicated geometries and loading cases are examined to demonstrate the efficiency and validity of the new method.The results obtained by this study are compared with those reported in existing literatures and it can be concluded that the DFPSO can perform well for the complex optimization problems.