To study the seismic performance of coal gangue concrete beam column joints, six full-scale specimens were prepared and subjected to low-cycle repeated loading tests. The analysis focused on various seismic indicators, including failure modes, hysteresis curves, skeleton curves, stiffness degradation, energy dissipation capacity. The effects of coal gangue aggregate replacement rates (0,0%, 50% and 100%) and beam longitudinal reinforcement ratios (0.67%, 1.34%, and 2.09%) on the seismic performance were studied. The results showed that the failure modes of joints are bending failure at the beam end and shear failure at the node area. The failure primarily manifests as extensive cracking in the joint area and significant spalling of concrete at the beam ends, with coal gangue concrete beam-column joints exhibiting more severe damage compared to ordinary concrete. Specimens with low coal gangue replacement rates displayed full hysteretic curves, slow stiffness degradation, good ductility, and good seismic performance. As the replacement rate of coal gangue increases, the specimens exhibits a pronounced pinching effect in the hysteretic curves, along with accelerated stiffness degradation and reduced ductility and energy dissipation. Increasing the longitudinal reinforcement ratio of the beam can improve the damage to the concrete at the end of the beam and enhance its bearing capacity. However, excessively high reinforcement ratio may induce shear failure of the nodes, reducing their energy dissipation capacity and ductility.