Soil and rock mixtures are commonly used as subgrade fill materials for mountain airports. When subjected to cyclic loading, they experience cumulative deformation, leading to uneven settlements that can compromise the stability of the upper foundation. To understand this deformation pattern, a series of dynamic compression tests was conducted on soil and rock mixtures. The study analyzed how the specimen's cumulative deformation changed with the number of cyclic loads across different stone contents and confining pressures, and it developed a corresponding mathematical model. Results showed that, at a fixed stone content, higher confining pressure resulted in greater maximum axial cumulative deformation, with the rate of increase accelerating as stone content increased. The deformation curve typically has two phases: an initial rapid accumulation of axial deformation during cyclic loading, followed by a slower growth as the specimen densifies. Based on these findings, a simple model describing the law of cumulative deformation was proposed, which aligned well with experimental data. The study also examined how excess pore water pressure in saturated specimens evolves during cyclic loading, noting its rapid buildup and slow dissipation, providing valuable insights for managing differential settlement and assessing the stability of mountain airport subgrades.