Abstract: Through the static loading test of 8 prestressed-concrete composite slabs with concrete-filled tubular steel trusses connected by close joints, the flexural behavior of the composite slabs in vertical direction of being prestressed was studied under uniformly distributed load, and the plane section assumption was verified. The results showed that the work performance of prestressed concrete composite slab with concrete-filled tubular steel trusses was good. The cracks of double-piece composite plate only appearred at the joint in the middle of the span, while the cracks of triple-piece or quadruple-piece composite plate appear closed. The anti-crack bars of joints had little effect on the improvement of cracking load, but they could share the stress of transverse stress reinforcement, significantly made the crack distribution evenly. The ultimate lood increased with the increase of the lamination thickness. The composite slab far away from the joint was in line with the assumption of plane section. Based on parametric analysis, the main influencing factors of bending stiffness in the vertical prestressing direction of the composite slab were analyzed as follows:the ratio of thickness of the prefabricated plate to that of the composite slab h/H and the width of the prefabricated plate b. Through nonlinear surface fitting, a formula for calculating the influence coefficient of vertical prestress direction stiffness was presented.