Transpiration cooling is considered to be one of the most effective cooling methods for protecting components from ablation in extremely high temperature environments, so improving transpiration cooling efficiency is quite useful in practical applications. Living creatures always have the optimal properties for cooling after long-term evolution. This study proposes a novel transpiration cooling concept using a biomimetic non-smooth surface inspired by the earthworm's rough skin. The transpiration cooling efficiencies of porous plates with three different bio-inspired non-smooth surfaces - isosceles-trapezoid, right-angled-trapezoid and parallelogram grooves -are numerically investigated. The numerical model is validated by experimental data. The structure of the non-smooth surface dramatically affects the film thickness and surface heat convection intensity of transpiration cooling. The cooling efficiency is significantly improved by the parallelogram style non-smooth surface. The bio-inspired non-smooth surface successfully thickens the protective film and achieves a significantly better cooling performance. The protective film of transpiration cooling is thickened 22.7% while the transpiration cooling efficiency is significantly increased by 12% with the assistance of the bio-inspired non-smooth surface.