The excavation-induced horizontal movement of soil behind retaining wall is analytically deduced based on displacement-displacement boundary problem under plane strain condition. With respect to two basic modes of wall movement, i.e. translation and rotation about toe, the exact theoretical solutions to horizontal movement of soil behind wall are provided. Specifically for incompressible soil, this theoretical solution has been validated by comparing to the classical Source-Sink theory. It has been indicated that horizontal movement of soil behind retaining wall depends essentially on the mode and magnitude of wall displacement and independent of Young’s modulus of soil. As for incompressible soil, the present theoretical solution may result in well consistent predictions with the classical Source-Sink method. However, Source-Sink method always provides an approximate solution, which tends to underestimate the horizontal movement of soil around the deep position with maximum wall displacement, and overestimate that of soil around the deep position with minimum wall displacement.