Abstract: In order to avoid the adverse effects of local buckling of one castellated beam, the influence of opening parameters on the local buckling of the web of the beam should be clarified and the limit of height-thickness ratio of the web should be determined. The effects of floor, of opening ratio of the web, of transverse stiffener and, of the height-thickness ratio of the web on the failure modes, on the bearing capacity, on the ductility and, on the energy dissipation of the castellated beam under static and reciprocating loads were studied by means of test and finite element analysis. Developed is one formula for calculating the shear buckling coefficient of the perforated plate considering its hole-diameter to height ratio, the opening shape of the hole, the boundary conditions and, the limit height-thickness ratio of the castellated beam without elastic-plastic buckling. The results show that the buckling of the web is delayed by the combined action of the slab of the castellated beam, that the stiffener can avoid the buckling of the web, and that the increase of the opening rate makes the opening angle more easily enter the plastic stage and form the plastic hinge failure mode. With the increase of the web height-thickness ratio (48.0~85.3), the bearing capacity and ultimate displacement are decreased by 43% and 33%, and the ductility and energy consumption are decreased by 15% and 36%. When the hole-diameter to height ratio varies from 0.2 to 0.8, the limit of thickness ratio of castellated steel beams with circular and hexagonal perforated plates is 79.7~48.4 and 76.7~47.0 times of steel number correction factor.