Abstract: A novel shear damage model based on homogenization theory and a modified Mohr-Coulomb criterion is proposed to predict the full deformation process of gas hydrate-bearing sediments (GHBS) during shearing by analyzing micro-mechanisms of shear deformation and failure characteristics. Then, the physical significance of the model’s parameters is explored. Finally, the damage evolution and shear stress partition inside GHBS during the shearing process are analyzed in detail. The results show that model parameters have clear physical meaning, and the shear damage model is capable of reflecting the nonlinear deformation and strain softening characteristics of GHBS due to its ability to better describe the damage evolution and shear stress partition mechanisms inside GHBS during the shearing process. Comparisons of experimental and theoretical results show that the global performance of the novel shear damage model is satisfactory. The model is expected to be widely adopted to analyze submarine landslide instability due to hydrate dissociation.