By using homemade shear equipment

the shear tests of rock mass which has natural discontinuities from the Three Gorges reservoir area are carried out under different states; the deformation and intensity curves of different models are drawn. After analyzing the experimental data we conclude that the shear strength of discontinuity is relevant not only to positive stress but also to water content of the discontinuity of the rock mass; that is

the shear strength rise with the rise of the positive stress and decrease with the rise of water content. Finally

we compare the shear strength parameters which with the theoretical data

and find the two groups of data are consistent. The paper also proves the experimental device and method are feasible and valid in engineering application.