Abstract: Based on the experimental study of two ultra-high performance concrete (UHPC) steel truss composite slabs and a concrete slab,the effect of steel truss on the flexural behavior of the UHPC composite slabs,such as deflection, cracks and concrete strain,was analyzed.And the secondary loaded effect of the UHPC steel truss composite slabs was investigated.The study showed that the UHPC steel truss composite slabs had better flexural behavior than ordinary concrete composite slabs.The section strain basically conformed to the plane hypothesis,the ductility was better, and the secondary stress was not obvious.The steel truss could effectively enhance the overall flexural bearing capacity of composite slabs, and weaken the phenomena of "stress excess" of tensile steel and the phenomena of "strain lag" of compressive concrete. The results, which were calculated by the formula of flexural normal section bearing capacity of steel truss UHPC composite slabs, agreed well with the experimental data when the equivalent tensile effect coefficient k₃ of concrete was 0.35.