In order to investigate on the tension crack occurring in the upper surface of rock slopes, barodynamics experiment using models representing rock slope was performed, and tensile strain on upper surface was measured. Results obtained by this experiment were examined by elasto-plastic analysis using FEM. By both barodynamics experiment and theoretical analysis following conclusions were obtained:(1) In case of vertical slope, horizontal strain near upper surface is always tensile strain, and its magnitude increases as slope height increases.(2) In case θ≦80℃, horizontal strain near the upper surface is compressive strain when slope height is small. As slope height increases, compression failure near the toe of slope causes increase in compressive strain near the upper surface. When slope failure occurs the horizontal strain near the upper surface suddenly turns into tensile strain. By these facts, it can be seen that slope failure occurs progressively from the toe of slope.