Partial or complete replacement of non-renewable composite materials with natural fiber reinforced polymer composites, such as basalt fiber, carbon fiber and glass fiber reinforced polymer composite can reduce the consumption of non-renewable resources and damage to the ecological environment in civil engineering construction. It is of great significance for solving global warming, developing green manufacturing and low-carbon cities, and promoting sustainable development in civil engineering. Therefore, this paper focused on mechanical properties of ramie fiber reinforced polymer (RFRP) composites. Futhermore, the shear capacity of RC beams strengthened with ramie fiber sheet was studied, and the bearing characteristics and failure modes of RC beams strengthened with fiber reinforced polymer composites was analyzed. The results show that after the surface treatment with dilute hydrochloric acid, silane coupling agent (KH-550 and KH-560) and aluminum zirconium coupling agent, the mechanical properties of RFRP composites enhanced significantly. Moreover, the surface wettability and interfacial properties of ramie fiber to the epoxy resins were improved by about 40 %. The shear strength results show that after the reinforcement of ramie fiber sheets, the bearing capacity and mid-span deflection of RC beams were greatly improved, and the silane coupling agent (KH-560) modifying ramie fiber sheets had better reinforcement than other fiber sheets. It could be concluded that the replacement of ordinary fiber sheets by ramie fiber sheets can not only reduce the consumption of non-renewable resources, but also improve the shear resistance of RC beams strengthened with the fiber sheets.