Abstract: There are few studies on the constitutive model of bio-cemented calcareous sand. In this paper, the statistical damage constitutive model of bio-cemented calcareous sand was established based on the Lemaitre strain equivalence theory. The model assumed that the microelement strength of bio-cemented sand obeys the log-normal random distribution and the D-P criterion. The parameters S₀ and F₀ in the constitutive model were determined by the experimental data, and their physical significance were discussed. The theoretical results of the model were compared with the experimental results to verify the reasonableness of the model. Finally, the evolution of the damage variable(D), parameter S₀ and F₀ were analyzed with different calcium carbonate content. The results show that: The parameter F₀ reflects the limiting strength characteristics of MICP-treated calcareous sand, and the parameter S₀ represents its brittleness and ductility characteristics. The higher the level of cementation, the faster the damage rate and the larger the damage value. The damage variables eventually reaches a stable value as the axial deformation increases. The model can reflect the strain softening and strain hardening phenomena well, which can also represent the shear expansion and shear contraction characteristics of the volume strain curve. The research can provide some theoretical support for the engineering application of MICP-treated calcareous sand.