Abstract: In order to study the effect of dry-wet cycles on the shear mechanical properties of mica quartz schist, taking the mica quartz schist widely distributed in Northwest Hubei as the research object, the deterioration and failure mechanism of rock mechanical properties under different dry-wet cycles times were analyzed through direct shear test. The results showed that, the shear properties of mica quartz schist deteriorated obviously under dry-wet cycles, and the degradation rate of mica quartz schist was faster and larger in the early stage of dry-wet cycles, and slower and lower in the later stage. After 20 dry-wet cycles, the degradation degree of peak shear stress of mica quartz schist under different normal stress was 16.27% ~29.59%, and the degradation degrees of cohesion, internal friction angle were 26.58% and 15.36%, respectively. So the cohesion was more sensitive to dry-wet cycles. Lastly, based on Lemaitre damage theory and statistical damage constitutive model, the damage degradation model of mica quartz schist shear strength was established, and the relative error between the predicted values and the experimental values of peak shear stress were 1% ~6%, which can effectively predict the shear strength of mica quartz schist under different dry-wet cycles.