Abstract: Some properties of SH waves in layered media are analyzed such as propagating path, reflecting cofficent and travelling time in order to improve the accuracy and efficiency of 1-D finite element method dealing with seismic response problem of horizontal layered site for inclined SH waves in time domain. Based on the Huygens wave principle, impedance interfaces are regarded as the secondary sources or wavelet sources, which are called interfacial wavelets. The relation between interfacial wavelets can be expressed as a group of time delay equations, and the motion of interfaces can be obtained by solving the time delay equations. The earthquake motion can be ascertained from surface wavelets. The new method is called an interfacial wavelet algorithm and demonstrated by two corresponding numerical models. When using this method, mesh divisions and artificial boundary conditions need no treatment so that computing amount and transmission errors between nodes are reduced greatly. It is very fit to solve seismic response in layered media.