Abstract: The deformation of backfill is mostly in the post-peak deformation stage in the actual stress environment of the mine. It is important to study the post-peak strength characteristics of backfill. Uniaxial compression test of backfill with cement-sand ratio of 1∶6, 1∶8 and 1∶10 were conducted. The deformation and failure characteristics of cemented backfill with different ratios were analyzed, the higher cement-sand ratio of the backfill, the higher peak strength and residual strength. Based on statistical damage theory, a damage variable of backfill is established. A new damage constitutive model which can simulate the full deformation process of backfill is established by modifying the damage variable. All these model parameters analytic solutions are deduced by the geometric features of uniaxial compression test curve. The smaller the α, the higher the residual strength of backfill, the greater the F0 and m, the greater the peak strength of backfill. The different cement-sand ratio of damage evolution are analyzed, different cement-sand ratio of backfill damage in an S-sharped growth model and low cement-sand ratio of backfill can withstand greater deformation, and better play to its bearing capacity. The result shows that, this model can describe the characteristics of the complete stress-strain curve and the post peak residual strength of cemented backfill very well, and provide reference for the design of backfill.