Based on the limit equilibrium theory and the failure model of grillage supporting structure with prestressed anchor
using Bishop method for slope stability
and considering vertical inter-slice shearing force effects on the shear strength of soil side-slope
the search model of the most dangerous slip surface is set up; ann the solving formula of stability factor is derived; calculation of integral stability of slip surface has been carried out by using the genetic algorithms. The method can avoid getting in local minimum in optimal design; and it has more credible and accurate advantage.