In order to study the coupling mechanism of rock stress field-seepage field under triaxial continuous loading conditions, the seepage tests of red sandstone with different pore water pressures were carried out to analyze the mechanical response and seepage characteristics of red sandstone under fluid-solid coupling. The particle flow numerical simulation and Fipy coupling method were used for experimental verification and meso-interpretation. The development, propagation and seepage evolution of rock cracks under fluid-solid coupling were revealed, and the influence mechanism of effective confining pressure on volumetric strain, meso-fracture and seepage was clarified. The results show that : (1) According to the crack volume strain, the total stress-permeability coefficient-strain curve of red sandstone under pore water pressure is divided into four stages : I-compaction seepage retardation stage, II-elastic deformation seepage stability weakening stage, III-crack propagation seepage instability enhancement stage, IV-post-peak fracture sliding seepage reduction stage. (2) The smaller the effective confining pressure of rock is, the easier the force chain and crack are to break and initiate, and the easier it is to produce macroscopic fracture. (3) Due to the different pore structure and crack distribution in different areas of the rock, there are some differences in the distribution of permeability coefficient. (4) The seepage velocity and permeability coefficient are positively correlated with the degree of crack development. The seepage path of rock is closely related to the initiation, propagation and penetration of microcracks, and a continuous and relatively stable seepage path is formed in the fracture surface.