Abstract: The flexible retaining method with prestressed anchor has obvious advantages of low cost, quick and convenient in construction and great safety performance for deep and ultra-deep foundation pits in rocky soils. Its economic and social benefits are significant. Numerical simulation analysis is conducted for the deep foundation pit of Dalian Victory Square using the FLAC software. The influence of different anchor prestress forces on the mechanical behavior of foundation pit is mainly studied. The results show that the greater the prestress, the smaller the horizontal deformation of the foundation wall and the vertical settlment of the ground for small prestress force. The increasing prestress force does not further reduce the horizontal deformation and the vertical settlement for greater prestress force. The prestressed anchors can effectively reduce the maximum shear strain increment in the rock body and delay the onset of shear sliding failure of the foundation pit to a certain extent. There is a reasonable threshold value of anchor prestress force for the foundation pit. The proposed design method and numerical simulation results may provide great guidance for the promotion and application of flexible retaining method with prestressed anchor.