Abstract: This paper studies an input method of oblique plane seismic waves for three-dimensional calculation, which is based on a time-domain wave method coupled to an explicit finite element method with viscous-spring artificial boundary conditions. Application of this method to seismic responses of the Xiaowan arch dam under SV waves of oblique incidence is also examined. The results indicate that the responses of this dam are significantly different from those under P waves. The incidence angles of SV waves can cause more sensitive responses of displacement spectrum in low frequency domain, a range crucial to aseismic safety. Under incidence in stream direction the amplitude magnification coefficient of displacement spectrum is significantly decreased by an increase in its angle, while under incidence in transverse direction the coefficient is significantly increased.