The change of typical bank slope’s water occurrence environment and the special climatic condition of dry hot valley in Wudongde reservoir area will make the shear characteristics of jointed rock mass on bank slope deteriorate continuously. Based on this, the shear test of joint surface under heat-wet cycles is carried out. The results show the following. (1) The shear strength and joint roughness deteriorate significantly with the increasing test cycles, and the deterioration ranges are 70.90%–84.48% and 29.33%–61.56% in the first 5 cycles. (2) The shear strength’s deterioration caused by repeated shear is mainly in the initial state, and the shear strength’s deterioration caused by heat-wet cycles increases firstly and decreases later with the test cycles. (3) By introducing the equivalent damage coefficient of morphology, the shear strength calculation formula is improved, and it can be seen that the estimated value coincides with the modified test value. The research results can provide a reference for long-term variation and calculation method of joint surface’s shear strength under different water-rock interactions.