This paper presents a fundamental research in the mechanical properties of the regular jagged discontinuity under various normal stresses in the shear test. The mechanical properties of the regular jagged discontinuity under shear stress and their principal regularities are described. The strength and roughness of discontinuity under shear stress are investigated by the analysis of the data obtained. The calculation of shear stiffness of discontinuity and an empirical formula between the slope angle and roughness coefficient of discontinuity are proposed. The changing regularity of the parameters of the shear strength of discontinuity under shear stress is investigated, and an empirical formula is established to evaluate the shear strength of discontinuity.