Abstract: The Jurassic formation in Three Gorges Reservoir is typical of soft-hard alternating strata, which has its special engineering geological characteristics such as strong hydrophilicity, weak permeability. This paper selects four different kinds of structural plane for the study, and has carried out the basic research on its mechanical properties by different normal stress indoor direct shear test. Through statistical analysis of test data, shear-normal relationship graph and stress-shear displacement relationship curves of various kinds of structural plane under the effect of different normal stress were drown, four different shear strength parameters of the structure were obtained. shear characteristics were studied, Then we can give the preliminary judgment about instability plane in slope, and provide reliable reference for the later slope stability evaluation.