To investigate the effect of ductile material on strength and ductility improvement of concrete, the flexural performance of LSECC-Concrete composite beam, in which the ductile fiber reinforced cementitious composite with characteristic of low shrinkage (LSECC) was used at the tensile part of the beam, was studied by both experiments and theoretical simulation. The results show that the concrete beam combined with ductility material at the bottom of beam can achieve a high ductility and enhance load carrying capacity. The strength of the LSECC and plain concrete, as well as the thickness of LSECC layer used in the composite beams can greatly influence the strength and ductility of the beam. Based on cracking strength criteria and stress-crack opening relationship, a model to simulate bending performance of composite beam is developed, which can well predict the flexural behavior of composite beam. A seasonable agreement between model and test results is observed and the model may be used in optimization of the composite structures.