As a typical soft rock material, the mechanical behavior of mudstone under uniaxial compression is of crucial significance for the stability assessment of tunnels and underground engineering. A multi-scale analysis method combining laboratory tests with PFC^2D particle flow discrete element simulation was employed to systematically investigate the mechanical properties and failure laws of mudstone, and to reveal the macro-mesoscopic mechanisms of mudstone failure. A parallel bond model applicable to rock masses was constructed based on the PFC^2D software, and the accurate reproduction of macroscopic mechanical responses was achieved through mesoscopic parameter inversion.The research results indicate that the stress-strain curve of mudstone exhibits distinct four-stage characteristics: compaction, elasticity, plasticity, and post-peak softening. Microcracks begin to initiate during plastic deformation and develop rapidly after the peak stress. The synergistic verification from three aspects—stress evolution, displacement evolution, and pore distribution—collectively reveals the apparent characteristics of macro-mechanical responses influenced by mesoscopic failure mechanisms. The process of rapid crack propagation is accompanied by the dissipation of elastic compressive strain energy and cementation energy, as well as the accumulation of damping energy and sliding energy. The “experiment-simulation” collaborative analysis method established in this study provides effective support for the stability analysis of mudstone engineering.