Abstract: Aimed at several disadvantages such as partial search, the fixedness of the value of reflection factor and the ignorance of the complex diversity in the approach of the basic complex method, the corresponding improvements upon the above disadvantages defined as dynamic full reflection and retraction operator and the rule of most redundant design point to be reflected are presented. Not only the information of the design space but also the objective function value is utilized to determine the redundant design point. The basic complex method and the new kind of complex method are respectively employed to locate the critical failure surface with true minimum factor of safety of non-homogeneous soil slope , and the comparison of the results has shown that the percent of successful run of the new complex method is higher than that of the basic complex method.