A discrete-continuous coupling analysis method based on FLAC2D/PFC2D is established with the help of the program’s own FISH language and Socket O/I data transfer interface. According to the statistical characteristics of the mesostructure of the slope site, the computer stochastic simulation method is used to construct the mesostructure model of the soil–rock mixture in the discrete domain. The deformation and failure mechanism of the SRM slope is studied by using the established discrete-continuous coupled analysis method. The results show that the statistical distribution of the mesoscopic contact characteristics (such as contact direction and contact force) between soil and rock particles inside the slope changes and adjusts significantly. Among them, the main direction of the statistical distribution is adjusted most significantly, and the main direction is finally adjusted to being basically the same as the sliding direction of the slope. The change in the mesoscopic contact characteristics between soil and rock particles is the internal driving factor for the macroscopic deformation of the slope and the adjustment of the stress state.