The spray-applied method, as a significant technique in trenchless rehabilitation, has been widely applied in engineering practice. A systematic study was conducted on the application effectiveness of ultra-high performance cementitious composites(UHPC) in spray-applied rehabilitation of reinforced concrete curved beams, with particular focus on the influence mechanisms of key parameters including curvature angle, rehabilitation thickness, and interface configuration on the load-bearing performance of rehabilitated structures. Experimental results reveal that curved beams with 90° curvature angle demonstrate greater suitability as test specimens compared to those with 120° curvature. When employing UHPC for rehabilitation, specimens achieve undamaged strength equivalent to original components at a rehabilitation thickness of 5 mm, while bearing capacity enhancement exhibits approximately linear positive correlation with rehabilitation thickness. Furthermore, natural bonding interfaces display adhesive performance degradation under sustained loads, leading to structural system transition from composite to combined structures. Notably, nail-planting treatment significantly improves interfacial bonding performance, achieving 1.7 ~ 1.8 times higher interfacial bond strength than natural bonding, effectively prolonging the composite state duration and substantially enhancing load-bearing capacity. Conversely, plastic film adhesion weakens interfacial bonding effects, resulting in reduced bearing performance.