Abstract: The mechanical properties and stability of shallow rock mass in Three Gorges Reservoir area are significantly affected by climate and environment conditions. This paper examine the deterioration effect of cyclic temperature and humidity climatic environment due to diurnal variation on the weathering damage and mechanical properties of silty mudstone. The standard rock samples processed from silty mudstone are subjected to different numbers of high-low temperature and humidity cycles. Then the mechanical properties under uniaxial compression are tested to analyze the stress-strain curve, strength, deformation, fracture properties and energy characteristics. The results show that, with the number of temperature and humidity cycles increasing from 0 to 5, the uniaxial compression strength, elastic modulus, deformation modulus, total energy, elastic energy and its proportion of silty mudstone are linearly and negatively correlated with the number of temperature and humidity cycles. The values are decline by 49.21%, 53.11%, 57.78%, 42.29%, 58.7% and 32.45%, respectively. The dissipated energy and its proportion are positively correlated with the cyclic number, and their growths are 80.86% and 215.27%, respectively. On the mesoscopic scale, the bonding force between silty mudstone particles after cyclic temperature and humidity treatments is weakened, leading to the decrease of strength, the increase of brittleness and the reduction of viscosity between particles. The amplitude of variation is positively correlated with the number of temperature and humidity cycles. Meanwhile, the reduction amplitude of bonding force between particles is not uniformly distributed in the rock mass, but shows a certain gradient variation from surface to interior, and the closer to the surface, the greater the reduction amplitude. These changes make it is easier to produce tensile airfoil cracks or oblique tensile-shear mixed airfoil cracks due to transverse expansion of silty mudstone specimen under uniaxial compression. The specimen is even more incomplete. On the macroscopic scale, the silty mudstone shows lower brittleness and higher plasticity after cyclic temperature and humidity treatment.