Arching effects easily occur for a concrete face rockfill dam(CFRD)built in a narrow valley. In this paper, the Maerdang power station engineering was used for a case study. 3D finite element models of the CFRD under different valley slope schemes were established. Distributions of the static and dynamic displacement, stress of the dam under different slope angle schemes were obtained by finite element(FE)analysis. In addition, the effect of slope angles on the stress and deformation characteristics of the dam was analyzed. Meanwhile, the influence of the valley slopes on the structure stability of the dam under earthquake action was studied. Results indicate that the valley slope is approximately 50°when evident stress arch effect occurs inside the rockfill of the dam so that the critical angle of the valley should be 50°. A negative correlation is observed between the slope angles and the dam settlement. In the situation of arching effect, the earthquake action has no significant negative effects on the dam.