In order to study the effect of joint structure on the mechanical performance of densely assembled pre? stressed reinforced concrete composite slabs, an enhanced tight joint details is proposed, and the flexural tests of three groups of composite plates were designed. The test systematically studied the bearing capacity, stiffness, failure mode, crack and deformation performance of each group of specimens, and the joint force transmission performance of the jointed laminated slab as well as the two-way mechanical characteristics of the prestressed composite floor are analyzed. The test results show that the enhanced tight joint can improve the flexural stiffness of the composite slab in the vertical direction of the joint, its bearing capacity is close to that of the cast-in-place slab, and it can ensure the effective load transmission at the joint. The crack morphology at the joint position is good when the joint plate speci? men fails, and no tear damage occurs along the composite surface. The bearing capacity and deformation performance of the prestressed composite slabs are good. The mechanical performance test of the prestressed composite floor fur? ther shows that the composite slab with the reinforced joint structure can carry out two-way load transmission. An ul? timate bearing capacity formula of the prestressed composite floor was established based on the principle of virtual work. The calculated value of the ultimate load is good in agreement with the experimental value, which verifies the rationality of the assumed plastic hinge line mode. The strip method was used to verify the two-way mechanical per? formance of the prestressed composite floor.