Abstract: Ultrahigh toughness cementitious composites material with strain-hardening characteristic (UHTCC) was recently developed in China. In this paper, 12 steel reinforce UHTCC (RUHTCC) beams with different reinforcement ratios are categorized into 4 groups and tested under four-point bending loading. The flexural load-carrying capacity at initial cracking, yielding and ultimate failure is calculated based on beam theory and the ductility of RUHTCC beams is calculated in terms of middle-span displacement, curvature and energy, respectively. A comparison between the theoretical and experimental results demonstrates well agreement, and it is found that RUHTCC beam can enhance the ultimate flexural capacity and ductility of ordinary reinforced concrete beam and save the amount of steel reinforcement. These observations suggest that UHTCC is a promising alternative material to conventional plain concrete material for some parts where either heavily reinforced stirrups are in need or high ductility is desired, i.e, anchorage zone in pre-stressed structures and beam-column joint.