Abstract: The hybrid fiber-reinforced concrete was prepared by using the polyethylene fiber ( PE) of a high elastic modulus and the polypropylene synthetic fibers( CPP) of a low elastic modulus，and its flexural behaviors and compressive resistance were determined． Then，the significances of the factors influencing the flexural toughness were discussed through a two-factor variance analysis，and the toughening mechanism of the hybrid fiber was explored． The results show that ( 1) the compressive strength of hybrid fiber-reinforced concrete specimens with different coarse aggregate contents is generally higher than that of plain concrete，and the improvement ranges are mainly between 15% ～ 30% ; ( 2) the load-deflection curves of the concrete specimens with the hybrid fiber are relatively full; and，furthermore，most curves exhibit a slow deformation softening characteristic while some display a deformation hardening characteristic; ( 3) the fiber content has a significant effect on the toughness of the concrete， while the coarse aggregate dosage has a smaller one; and ( 4) the CPP /PE fiber can toughen the concrete from different hierarchies，which causes a positive hybrid effect，thus enabling the prepared hybrid fiber-reinforced concrete to possess excellent toughness．

Key words: hybrid fiber, concretes, mechanical properties, flexural toughness, two-factor variance analysis, fiber content