Abstract: Based on the Goodman element and the concept of the thin element proposed by Desai, a new type of thin layer element is presented. This thin layer element can simulate the static and dynamic characteristics of soft interlayer. Utilizing a hybrid iteration scheme, the adjustments of overloading stresses and overlapping are implemented simultaneously and efficiently, so the speed of iteration is enhanced. Employing the present thin layer element, the seismic stability analysis of a gravity dam is performed. The results show that the dynamic stability of the gravity dam is controlled by a soft layer T₃^2-3 in front of the gravity dam and corresponding safety factor is 2.50 approximately.