The invention relates to the technical field of concrete dams, in particular to an orifice flood discharge structure in a concrete dam. The structure comprises an orifice steel liner arranged along awater flow direction, wherein a concrete structure is poured around the orifice steel liner, the orifice steel liner comprises a plurality of steel liner sections which are sequentially connected andarranged, and the steel liner sections each comprise a top plate, a left side plate, a bottom plate, a right side plate, a first connecting folded plate, a second connecting folded plate, a third connecting folded plate and a fourth connecting folded plate. Welding seams formed by welding of the components are butt welding seams, the butt welding seams are more convenient for groove cutting and welding construction compared with fillet welding seams formed by welding in the prior art, the thickness of the periphery of the butt welding seams is consistent, the welding quality and reliability are improved, a detection operation surface is a plane, and the detection of the welding quality is also convenient. Moreover, the four corner edges of the steel liner sections are not right angles, sothat the problem of stress concentration at the four right-angle corner edges is avoided, the concrete structure is more favorable for vibrating and compacting, and the construction quality is improved.