Abstract: Defining the most dangerous failure surface in slope stability analysis is a key point.Genetic algorithm is a global optimization algorithm.Compared with the general optimization method it avoids local minimum value.Generally in the practice project the geometrical form of the slope is irregular and the material is heterogeneous, not all the shapes of the real critical failure surface can be described accurately as circular arc, so it is necessary to study the stability of the slope with arbitrary-type failure surface.In order to analyze the slope stability more ra-tionally, the article uses genetic algorithm to search and simulate the critical failure surface in practice, and a non-circular failure surface is got.The comparison of results of the practice project approves that the method is more precise and more adaptable.