According to the basic solution of semi-infinite elasticity subjected to horizontal loading presented by Muki, boundary conditions and continuous conditions between layers, the basic solution for twolayer elastic half space was derived. The displacement and stress of arbitrary point within the elasticity were also inferred. Thus, exact working property of laterally loaded piles will be obtained by applying these solutions. Several numerical examples were given. The results are well coincident with Mindlin's solution and Davies & Banerjee's computing results.