<p>Pre-existing and engineering-induced fractures significantly weaken the mechanical properties of rock masses. Although the highly non-uniform distribution of contact stress induced by rough fracture surface is widely recognized, systematic understanding of its spatial complexity and mechanical consequences remains limited. This study innovatively integrates high-resolution 3D scanning with pressure-sensitive film testing to conduct multi-scale normal compression experiments on granite fractures, quantitatively characterizing the distribution patterns of contact stress and their impacts on normal deformation and damage evolution. Key findings include: The fracture contact ratio measured by the pressure-sensitive film demonstrates nonlinear growth with normal stress, exhibiting exponentially decaying growth rates at elevated normal stresses; contact stress fields display pronounced spatial heterogeneity—low-stress zones dominate spatially but contribute minimally mechanically, while clustered medium-to-high-stress regions progressively expand with loading; contact stress distribution exhibits scale-invariant characteristics. The stress redistribution effects mediated by asperity interactions and localized damage accumulation mechanisms driven by stress concentration combine governing fracture mechanical responses. These insights advance cross-scale modeling of fractured rock masses while providing quantitative criteria for stability assessment in geological repositories and engineered underground structures.</p>