In order to optimize the joint scheme of bidirectional loading truss reinforced concrete composite slab and improve its stress performance at the joint position, a new type of composite slab with the pocket joint is designed in this paper. Relative slip is easy to occur between the new and old concrete combined interface, which influence the global bearing capacity of the truss reinforced concrete composite slab, therefore, the composite surface sliding is considered in the stress performance studying of truss reinforced concrete composite slab using the finite element method in this paper. The influences of connection modes, thickness of cast-in-place layer and additional reinforcement on stress performance of composite slab are studied according to the numerical analysis of the cast-in-situ slab, composite slab connection without gaps and pocket joint composite slab. The results show that the new pocket joint can make the bearing capacity of truss reinforced concrete composite slab better, and guarantee the effective transmission of the force between the precursor layer and cast-in-place floor concrete, adding cast-in-place layer thickness can effectively improve the bearing capacity of a truss reinforced concrete composite slab, and the influence of additional reinforcing ratio on truss reinforced concrete composite slab bearing capacity is particularly obvious as well, so the bearing capacity of the slab increases with the increase of the additional reinforcement ratio within limits.