The shear strength of rock joint is the basis information to assess the response and safety of rock engineering in practice. Using the rock shear machine CSS – 342, a series of tests has been made on artificially cemented rock joint samples with varied morphology to investigate the influence of surface morphology on its shear strength. It can be easily found that the peak shear strength increases with increasing the normal stress and roughness. However, in the case of same surface morphology, the ratio of shear stress to normal stress decreases with increasing normal stress, indicating that the dilatancy angle caused by the morphology decreases with increasing normal stress. A hyperbolic function is proposed to describe the evolution of dilatancy angle under varied normal stress on the basis of a detailed boundary condition of dilatancy angle. In the current research, the tensile strength is used to capture the effect of intact rock. Then, a new empirical formulation is suggested to evaluate the peak shear strength of rock joint by using the slope root mean square. A comparison between the proposed empirical criterion and the famous Barton formula is also made. The results indicate that the calculated values by the proposed criterion are in good agreement with the measured ones.