Aiming to address the challenge of simultaneously ensuring both level alignment and sufficient seismic performance in the case of wing flange in externally extended cantilever spliced full-bolted connection joint beam, a novel stepped full-bolted connection beam-column joint is proposed. Low-cycle reciprocating loading tests were conducted on cantilever-type joint specimens with two different end-plate connection forms. A detailed analysis of failure modes, hysteresis curves, skeleton curves, bearing capacity, ductility, and energy dissipation capacity of the specimens was carried out to investigate the seismic performance of this type of joint. Furthermore, the influence of the connection form between the thick end-plate and U-shaped buckle on the seismic performance was analyzed. The test results indicate that different connection forms have a minor impact on the elastic segment performance of the joint but a significant impact on the ultimate failure mode of the joint. The stepped joint with a thick end plate exhibits good bearing and deformation performance, while the U-shaped buckle joint shows poor seismic performance. A finite element model was established and validated using the thick end-plate specimen. By changing parameters in the finite element software, the influence of end-plate thickness on the seismic performance of the new joint was explored. It was found that as the end-plate thickness decreases, the initial stiffness, bearing capacity, and energy dissipation capacity of the joint decrease accordingly.