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Abstract: The initial micro-cracks affect the evolution characteristics of macroscopic deformation and failure of rock but are often ignored in theoretical calculation, numerical simulation and mechanical experiments. In this paper, we propose a quantitative analysis model to investigate the effects of initial micro-cracks on the evolution of rock deformation and failure. The relationship between micro-crack propagation and sample failure characteristics was comprehensively studied by combining theoretical analysis with a micro-CT scanning technique. We found that with increasing confining pressure, the matrix elastic modulus of marble first increased and then tended to be stable, while the micro-cracks increased exponentially. The sensitivity ranges of the sample matrix elastic modulus and micro-cracks to confining pressure were 0-30 MPa and 30-50 MPa, respectively. The porosity and Poisson's ratio decreased exponentially. The increasing proportion of internal micro-cracks led to an increase in sample non-uniformity. The rock samples presented mainly shear failure under triaxial compression, and the failure angle decreased linearly with increasing confining pressure. The convergence direction of cracks decreased gradually. This quantitative analysis model could accurately portray the relationship between the overall macroscopic deformation and the deviatoric stress of samples at the compaction stage and the linear elastic stage. It is a useful tool to characterize rock stress-strain behaviors and for geological disaster prevention.