Abstract: To investigate the flexural performance of ultra-high-performance concrete (UHPC) frame beams reinforced with steel-FRP composite bars (SFCBs), an equivalent static test was conducted on 5 frame beams. In-depth analysis was carried out on the failure mode, on the crack, on the bearing capacity, on the deformation, on the strain response, and on the plastic rotational capacity of the frame beams. The effects of concrete type, of reinforcement type, and of beam-end reinforcement ratio on the flexural performance of the frame beams was studied. A three-dimensional finite element (FE) model of the frame beam was established and verified. Then, the steel ratio, the yield strength of the inner core steel bar, the elastic modulus of the FRP and the ultimate tensile strength of the SFCB were parametric analyzed. The experimental results revealed that the failure mode of all frame beams is the crushing of concrete at the beam-end and that the order of occurrence of plastic hinge is first beam-end and then mid-span. The substitution of normal strength concrete with UHPC significantly enhanced the flexural capacity, deformation, ductility, ultimate energy dissipation, and plastic rotational capacity of the frame beams while also inhibiting the generation and expansion of cracks. The plastic rotation angle of SFCB-UHPC frame beams was 4.9 times greater than those of steel-UHPC frame beams, demonstrating that the use of SFCB effectively enhances the beam-end plastic rotational capacity of the frame beams. A decrease in the beam-end reinforcement ratio significantly reduced the flexural capacity, ultimate energy dissipation, and beam-end plastic rotational capacity, while improving ductility. A formula was established for calculating the equivalent plastic hinge length, with the relative compressive zone height and effective section height of the beam-end controlling section as variables. The predicted values agree well with the measured values.