Abstract: A new type of fully assembled composite beam is presented in this paper, which includes precast concrete slabs, TJ fasteners (shear connectors), C-shaped steel channels and steel beams. It has the advantages of no on-site wet operation, low requirement on installation accuracy, partial replacement and capable of recycling. In order to study the mechanical properties of this new composite beam, six sets of specimens (a total of 12 push-out tests) were designed considering the difference in spacing of steel grooves, fastener pre-tightening force, fastener types, etc. According to the difference in screw caps, the fasteners are divided into two categories, A and B. The universal hinge at the screw end of type A is manufactured in the factory, while that of type B is a standard part made in Germany which is just screwed into the end of screw. With the experimental parameters, the finite element models of the fastener and the new composite beam were established for comparative analysis. The results show that the type A specimens exhibit good residual strength stability. The load slip curves of type B specimens are smoother than those of type A specimens, and they have distinct strength decreasing segments. The shear performance of shear connectors will not be weakened by the reinstallation of fasteners of the composite beam after they are dismantled. The shear performance of the fasteners can be improved if they are not disassembled and torqued again after being stressed. The shear performance of the specimens with 300 mm steel groove spacing is superior to that of the specimens with 450 mm and 600 mm steel groove spacing. The formulas for calculating the preload capacity of fasteners are in good agreement with the experimental results and the finite element simulation results. The established finite element model can simulate the shear resistance of fasteners well.