The stability analysis of rock slopes holds paramount importance in a multitude of geotechnical projects, including rock-fill dams, embankments, as well as natural and excavated slopes. Among the various failure modes encountered in rock slopes, planar failure is a significant concern. Numerical analysis employing the Mohr-Coulomb linear criterion is a conventional approach adopted by engineers to evaluate the likelihood of planar failure within rock slopes. Nevertheless, the shear strength behavior of rock masses is universally recognized to exhibit nonlinear characteristics, rendering the Mohr-Coulomb criterion a simplified representation of a more complex reality. To bridge this gap, a range of nonlinear shear strength criteria has been formulated, aiming to more accurately depict the nonlinear behavior of rock masses. The objective of this paper is to provide novel insights into the stability analysis of rock slopes through the application of the Ucar nonlinear criterion. The outcomes demonstrate that the Ucar criterion, when juxtaposed with other nonlinear criteria reported in scholarly literature, provides a more precise estimation of the potential failure wedge.