Fifteen specimens of the prestressed steel reinforced ultra-high strength concrete beams and three specimens of the prestressed ultra-high strength concrete beams were tested to investigate the flexural ductility of specimens. The test results indicated that: the encased structure steel increased the bearing capacity of specimens, and enhanced the ability of sustaining load after peak load of the specimens. The increase of effective pre-stretching stress, reinforcement ratio of structure steel, reinforcement ratio of ordinary longitudinal bar, and reinforcement ratio of prestressed tendon leaded to the decrease of displacement ductility factor, the decrease of depth of prestressed tendon and structure steel leaded to the decrease of displacement ductility factor. The effect of complex reinforcement index considering of reinforcement on displacement ductility factor were studied. By linear regression of test dates, the simplified calculation formula of displacement ductility factor was obtained, and complex reinforcement index was a single variable in this formula.