Ecological　slope　protection　offers　a　sustainable　solution　for　mitigating　rainfall-induced　geotechnical　failures.　In　this　study,　an　ecological　slope　protection　was　constructed　using　an　optimized　ecological　substrate　composed　of　red　soil,　organic　fertilizer,　cement　and　wood　chips　in　a　100:　20:　5:　15　ratio.　SEM　and　EDS　revealed　that　cement　effectively　anchors　red　soil,　improving　the　stability　of　ecological　substrate.　To　evaluate　rainfall-induced　performance,　an　artificial　slope　simulation　(ASS)　rainfall　model　with　a　cement-red　soil　ecological　bag　slope　was　developed,　complemented　by　a　small-scale　finite　element　simulated　slope　(FESS)　for　cross-validation.　The　results　demonstrated　strong　agreement　between　interlayer　pressure　measurements　in　the　ASS　and　FESS　numerical　simulations,　validating　the　high　accuracy　and　feasibility　of　FESS.　Based　on　the　validated　model,　a　full-scale　ecological-bag　slope　protection　FESS　model　was　conducted　on　an　actual　slope　to　investigate　the　effects　of　rainfall　intensity　and　slope　gradient　on　stability.　Under　low　rainfall　intensity,　slope　gradient　is　the　primary　factor　affecting　the　safety　factor.　However,　increasing　rainfall　intensity　reduces　the　safety　factor　through　progressive　matric　suction　loss.　In　the　case　study　under　the　historical　maximum　rainfall　intensity　of　378 mm/12 h,　the　computed　safety　factor　was　1.263,　meeting　the　three-level　slope　safety　requirements.　Consequently,　the　optimized　cement-red　soil　ecological　substrate　exhibits　exceptional　stability　under　extreme　rainfall,　providing　a　sustainable　alternative　to　conventional　slope　protection　systems　and　practical　design　guidelines　for　ecological　slope　engineering　in　rainfall-prone　regions,　contributing　to　enhanced　geohazard　mitigation.　©　The　Author(s),　under　exclusive　license　to　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature　2025.