Abstract: The evolution of pore-fracture structures in coal under high stress and high seepage pressure conditions is recognized as the fundamental cause of damage to its physical and mechanical properties. To ensure safe coal mining, the evolution characteristics of pore–fracture structures are investigated, and a damage constitutive model is required to predict deformation and failure behavior under multi-field coupling conditions. A series of hydromechanically coupled triaxial loading experiments with in-situ nuclear magnetic resonance imaging (NMRI) monitoring are conducted to obtain stress–strain responses and real-time evolution characteristics of pore–fracture structures in coal. A statistical damage constitutive model for the full deformation process of coal, incorporating post-peak residual stress under hydromechanical coupling, is established based on the Weibull function. The results indicate that the seepage pressure accelerates the accumulation of damage within pore-fracture structure, and the deformation and failure of coal are dominated by evolution of seepage pores and fractures (SPF). With the increase in axial strain, the variation rate of SPF exhibits a decreasing–increasing trend. The pore variation rate is introduced to characterize pore-fracture evolution and validate damage evolution trends, demonstrating the reliability of the proposed statistical damage constitutive model in describing coal failure processes. By integrating the SPF variation rate curve with the damage evolution curve, the stress-strain behavior of coal is identified as comprising four stages: damage-free loading, accelerated damage propagation, intensified damage development, and damage saturation. Further in-situ online monitoring reveals the consistency between SPF evolution and damage evolution, providing a method for validating statistical damage constitutive models based on NMR in-situ testing techniques. From the perspective of SPF evolution, the intrinsic damage mechanism and deformation–failure process of coal under hydromechanical coupling are clarified, compensating for the lack of direct physical structural damage characterization in conventional statistical damage constitutive models.