A local improvement procedure based on tabu search (TS) was incorporated into a basic genetic algorithm (GA) and a global optimal algorithm, i.e., hybrid genetic algorithm (HGA) approach was used to search the circular and noncircular slip surfaces associated with their minimum safety factors. The slope safety factors of circular and noncircular critical slip surfaces were calculated by the simplified Bishop method and an improved Morgenstern-Price method which can be conveniently programmed, respectively. Comparisons with other methods were made which indicate the high efficiency and accuracy of the HGA approach. The HGA approach was used to calculate one case example and the results demonstrated its applicability to practical engineering.