Abstract: To investigate the optimal replacement ratio of recycled coarse aggregates (RCA) in the precast base slab of composite slabs and to verify the applicability of the self-developed closely-spliced configuration (hereinafter referred to as “closely-spliced”), this study conducted experimental research on the material properties of recycled concrete. Comparative tests were performed on ordinary concrete and recycled concrete two-way closely-spliced composite slabs under four-edge fixed support conditions. The results indicate that the recommended optimal replacement ratio for RCA is 20%. Compared with conventional concrete two-way closely-spliced composite slabs, the recycled concrete counterparts also exhibited good ductility but slightly inferior cracking resistance. The use of recycled coarse aggregate had little effect on the ultimate load-carrying capacity and deflection of the two-way closely-spliced composite slabs. The final punching shear failure occurred near the loading points, and the performance of the closely-spliced configuration was equivalent to that of monolithic cast-in-place slabs. The closely-spliced configuration developed in this paper can be promoted for use in prefabricated structures to significantly improve the construction efficiency of composite slabs.