To investigate the seismic behaviour of the steel double-channel build-up member with reinforced concrete (RC) slab, quasi-static tests on four specimens with RC slabs were carried out under constant axially com? pressive load and reversed cyclic bending. The effect of the stitch spacing, the stiffener in plastic hinge region and the web depth-thickness ratio on seismic behavior of the testing specimens was studied. The experimental results in? dicate that all hysteresis curves are stable, showing excellent energy dissipation capacity and ductility. With the de? creasing stitch spacing, the strength and stiffness of specimens change insignificantly, but the ductility and energy dissipation capacity can be improved. The peak bearing capacity and initial stiffness of Specimen SJ3 are 28.42% and 22.70% higher than that of Specimen SJ1, respectively, indicating that the strength and stiffness of specimens can be improved by setting stiffeners in the plastic hinge region. The peak bearing capacity, ductility coefficient, initial stiffness and cumulative energy dissipation of Specimen SJ4 are 33.88%, 20.70%, 27.40% and 12.84% higher than those of Specimen SJ1, respectively, indicating that the seismic performance of specimens can be significantly improved by reducing the web depth-thickness ratio.