Abstract:A modified search strategy is presented to improve the global search ability of the basic complex method. A better design point can be located on the optimization line of each design point of the current complex respectively. Several new complexes are thus obtained by replacing each design point with its better design point. The new complex with the strongest diversity is the expected one in the current iteration,thereby defining a modified complex method,which is as straightforward as the basic complex method. The ability of the new complex method to find the global optimum is verified in the search of the critical failure surface with the true minimum factor of safety of two non-homogeneous soil slopes.