Abstract: Based on the Fredlund strength theory, a nonlinear strength criterion for unsaturated soils is proposed. The tensile strength envelope of the Fredlund strength theory as a result of extrapolation of compressive tests into the tensile regime is partially truncated or eliminated in the new strength criterion. The new tensile strength cut-off criterion (C-F criterion) allows to construct the failure mechanisms including rupture mode and shear deformation mode. Then a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions is put forward using the C-F criterion, and a uniform expression for the safety factor under nonlinear strength criterion is given. The influences of tensile strength cut-off and seepage on slope stability can be considered. The results show that the stability factors for infinite slopes in unsaturated soils with tensile strength cut-off are reduced compared to those based on the Fredlund strength envelope, with the largest drop for steep slopes particularly subjected to heavy rainfall infiltration.