<p>The bearing capacity and structural stability of natural rock mass are mainly governed by the existing weak joint surfaces. Most of the researches focus on the shear mechanical behavior of the joint surfaces under constant normal load (CNL) conditions. However, the mechanical characteristics of rock joints under dynamic normal load (DNL) in earthquakes are quite different from those of CNL conditions. Hence, the macro–micro shear mechanical properties and failure mechanisms of 3D rough joints under different normal dynamic amplitudes and frequencies are investigated using experimental and numerical calculation methods. The research results indicate that shear strength of rock joints under DNL conditions is significantly lower than that of CNL conditions for the same level of normal stress. The shear strength decreases linearly with the increase of normal load amplitude while it exhibits an exponential degradation with frequency. The shear stiffness of the joint surfaces depends on the normal stress under DNL conditions. As the normal stress and dynamic load amplitude increase, shear stiffness displays a decline tendency. Moreover, the influences of load frequency and amplitude on the phase deviation and shear slip characteristics are analyzed. The damage evolution characteristics and wear mechanism in the whole process of shear deformation are illustrated by numerical calculation methods. There is a positive correlation between wear quality and shear displacement in general. As frequency increases, the evolutions of the wear mass for joint surface gradually transform from linear to exponential increase and the wear region dramatically grows. The research results can provide valuable references for the further understanding of shear deformation and failure mechanism of rock joint surfaces under DNL conditions and mitigating corresponding geological hazards.</p>