The present study is to clarify the behaviour of sand under various combination of initial static and cyclic shear stresses and develop a model for evaluating not only cyclic shear strength but also cyclic residual strain during cyclic loading. As the results of cyclic triaxial compression tests, at first, it was found that the tendencies of pore pressure and axial strain were greatly affected by the reversal of cyclic shear stresses. In second, it was found there was a unique relationship between the residual shear strain and effective stress ratio at the end of each stress cycle. In third, a unique relationship was found between effective stress ratio and cyclic strength ratio which was defined by the ratio of the amplitude of cyclic shear stress and cyclic shear strength for a given number of stress cycles. A model which enables to evaluate the development of pore pressure and residual shear strain with various initial static and cyclic stresses was proposed based on the above findings.