By grating projection scanning system, the relationship between the roughness parameters and failure mechanism of marble was systematically studied. The final fracture surface was extracted and reconstructed through PFC3D. The surface characteristics were quantified and analyzed. The results show that Sa decreases linearly with the increase of the enclosure pressure under the loading path. The symmetry of the failure plane height of the rock sample under the high enclosure pressure condition is better than that under the low enclosure pressure condition. The Sa and Sku can better describe the distribution characteristics of the failure surface morphology under unloading path. Ssk does not change significantly with the increase of unloading rate. The roughness of the fractured surface is affected by the unloading rate and the initial enclosure pressure of the unloading process. The internal damage of the sample during unloading test deteriorates instantaneously and loss its bearing capacity instead of a gradual damage accumulation process.
