In order to effectively enhance the stability and safety of long columns under compression and seismic conditions while improving the recycling rate of waste concrete, a novel built-in H-shaped steel circular steel tube recycled concrete composite long column was proposed. By constructing 24 long column models and employing ABAQUS finite element analysis software with the PQ-Fiber subroutine, the influence patterns of recycled concrete strength, replacement ratio, and slenderness ratio on the mechanical performance under axial compression and seismic behavior under horizontal cyclic loading was investigated. The results show these as follows. Under axial compression, the composite columns primarily exhibit flexural-compressive failure with favorable ductility. Buckling failure occurs when the slenderness ratio reaches 39.6. The recycled concrete strength shows limited impact on bearing capacity, while increasing replacement ratio reduces bearing capacity-this effect diminishes significantly when replacement ratio exceeds 50%. Slenderness ratio demonstrates substantial influence on bearing capacity. Under cyclic loading, all specimens exhibit bulging failure with spindle-shaped hysteresis loops, slow stiffness degradation, and excellent energy dissipation capacity. It is concluded that the horizontal bearing capacity and energy dissipation increase with recycled concrete strength but decrease with higher replacement ratios and slenderness ratios. All configurations maintain displacement ductility coefficients between 3.0 ~ 3.5, indicating superior elastoplastic deformation capability.