Modular technology is driving innovation in the design and development of the next generation of nuclear power plants. Steel-plate concrete (SC) structure, characterized by their exceptional working performance and industrial construction efficiency, hold broad application prospects in modular structures. The SC wall-RC slab connection joint serves as a pivotal force transmission element between the SC module structure and the RC structure. and its connection joint design must ensure effective load-transfer performance and the modular construction feasibility. To investigate the shear performance of SC wall-RC slab connection joints, cyclic loading tests were conducted on two ‘thin-wall thick-slab type’ specimens employing different connection methods including rebar-coupler connection and additional shear keys as per GB/T 51340—2018 recommendations. All specimens suffered flexural and shear failure of the RC slab, with the primary failure path being from the loading end to the root of the RC slab. Remarkably, even without shear keys, the connection surfaces met shear resistance requirements. During testing, the straight-threaded rebar sleeves showed no signs of slipping, and neither the rebars nor the weld seams failed. Furthermore, the joint exhibited high ductility coefficients exceeding 4, indicating excellent load transfer behavior for the rebar-coupler connection. This suggests that the rebar-coupler connection can effectively serve as a connection method for SC wall-RC slab joints. However, the core region of the joint was identified as a shear weak zone. To meet full-strength connection design criteria, the volumetric steel ratio of tie-bars in the core region should not fall below 0.59%.