AbstractRamie fiber‐reinforced polymer (RFRP) composites are widely used in various fields owing to their environmental friendliness and cost efficiency. To understand the influence of different resin matrices on the mechanical properties and durability of RFRP composites under the same conditions and obtain better performance, ramie fiber‐reinforced phenolic resin (RFRPR) composites and ramie fiber‐reinforced unsaturated polyester (RFRUP) composites produced through compression molding were studied under hydrothermal conditions of 60°C with 50%, 85%, and 98% relative humidity for 3 months. The water absorption, tensile, flexural, and short‐beam shear properties were studied. The RFRPR composite had better flexural strength and short‐beam strength than the RFRUP composite. The saturated water absorption, water molecule diffusion coefficient, and retention rate of the RFRUP composite were higher than those of the RFRPR composite owing to the difference in the interfacial adhesion properties. The erosion of water molecules led to serious deterioration in the interfacial bonding performance of the RFRPR composite. It was found that the greater the humidity, the greater was the degree of interfacial degradation. This study lays the foundation for the further promotion and application of RFRP composites.