Soft mudstone dominates the rock mass at southwest Taiwan. Mudstone slakes significantly when it meets water due to a short diagenetic period and poor cementation. Gulleys are visible on the surface of mudstone slopes after rainfall. The low slaking durability resistance of the mudstone causes not only geographical badland but also erosion problems on the highway slopes in the mudstone area. An effective countermeasure for protecting the mudstone slope must contribute to a reduction in surface erosion; facilitate drainage from the slope surface during rainfall; and incorporate a high-strength structure to fight against swelling stress, preserve vegetation, and contribute to slope stabilization. In this study, a new slope erosion countermeasure, the soil-tyre-vegetation method (STV), was applied to an excavated mudstone slope in southwest Taiwan. STV utilizes waste tyres, H-beams, and geotextile. Waste tyres are good for preserving the soil for vegetation on mudstone slopes, mitigating slope erosion. The H-beams support the weight of the vegetation and the soil-filled tyres. The geotextile prevents the loss of fine-grain soil and guarantees drainage from the slope during heavy rainfall. The experimental results for a mudstone slope with a slope angle of 45A degrees showed that STV protected the mudstone slope and improved the condition of the vegetation on it.