The utility model discloses a waste boiler for a high-pressure boiler. wherein the waste boiler inlet and the waste boiler outlet are connected with the two ends of the waste boiler shell through waste boiler pipe plates respectively, the heat exchange pipes are arranged in an inner cavity of the waste boiler, the two ends of each heat exchange pipe are communicated with the waste boiler inlet andthe waste boiler outlet respectively, and the ascending pipe and the descending pipe are communicated with the inner cavity of the waste boiler respectively and form water circulation. At least one side of the waste heat boiler tube plate is provided with a protruding shoulder protruding outwards from the end face of the side in the axial direction of the waste heat boiler, and the protruding shoulder is annular. According to the waste boiler for the high-pressure boiler, a low-stress thick tube plate structure is adopted, that is, when a waste boiler tube plate forge piece is machined, at least one side of the waste boiler tube plate forge piece is provided with the protruding shoulder with a certain length, the length can meet the stress attenuation length, and the problem of stress concentration in the high-pressure state is solved. The waste boiler tube plate is designed to be a low-stress thick tube plate and is of a fixed structure, and the requirement for bearing high pressureis met.