Promoting the application of high performance material in modern bridge structures in order to meet the rapid development of high-speed railway technology, 10 pre-stressed reactive powder concrete (RPC)-normal concrete (NC) composite beams and 1 pre-stressed pure NC beam were designed and fabricated to investigate the flexural ductility of composite beams with the high performance material RPC, which was evaluated by the displacement ductility ratio at mid-span of composite beam. In this paper the effect of the height of RPC, the pre-stress ratio and degree of NC were mainly considered on the flexural ductility of composite beam. The results show that the sectional reinforced index decreases and the flexural displacement ductility ratio increases with the increasing height of RPC. Both the pre-stress ratio and flexural ductility increase with the increasing of steel strand number. The flexural ductility increases with the grade of upper NC as the brittle failure feature is not obvious. The deformation capacity of composite beam after the appearance of peak load increase, and the flexural ductility is significantly better than NC beam because of the excellent mechanical properties of RPC and the effect of steel fibers. It can be observed that the RPC has both high strength and good ductility. The fitting formula to calculate the flexural ductility of composite beams was proposed simultaneously based on the test results.