While the shear strength reduction (SSR) technique based on finite element method is employed to analyze slope stability

the safety factor of slope is dependent on the criteria used for evaluating critical instability condition. Due to the existing variety and uncertainty of the criterion

the rationality and uniqueness of the numerical solution of the safety factor are in doubt; thus

it is especially important to choose an instability criterion

which can not only meet with engineering need but also can facilitate its application. Firstly

a typical example slope is analyzed by using the elastoplastic FEM based on the SSR technique in order to examine the reasonability and applicability of various criteria

such as the abruptness of the displacement

deformation at a certain characteristic location

connectivity of plastic zone. Then

an improved criterion based on the criterion of displacement has been proposed by plotting the curve of displacement multiplying power to shear strength reduction ratio.