Of considerable importance in structural analysis is the transient response of a flaw to a time dependent stress field. A number of papers on the area of dynamic crack analysis have been reviewed in [ 1]. The impact response of a finite crack in plane extension has been considered in a paper by Sih and Embley [2]. Impact response of the interface crack is, however, a very complex problem due to the strong discontinuity of the material constants. The general elasticity solutions, that have been worked out for such a crack, involve oscillatory singularities which lead to wrinkling of the crack and overlapping of the materials [3]. These unreasonable phenomena have bothered scholars and research workers for a long time. In 1977, Comninou [4] proposed a frictionless contact model and solved the relevant static problem. The size of the contact region that is worked out according to the model is, however, too small to be acceptable to the assumption of continuum mechanics. In 1978, J.D. Achenbach [5] proposed another model which assumed that the crack faces are in adhesive contact near the tips. He solved the static problem and obtained some excellent results. The scattering of steady elastic waves by this kind of crack has been considered in a paper by Zhou Zhengong [6], and Rice [7] has further considered static contacting problems of the interface crack.