The invention relates to a tube-in-tube structure, in particular to a tube-in-tube structure for high-rise and super high-rise reinforced concrete core tubes and integrally-assembled space steel grids. The tube-in-tube structure comprises four steel frame columns which are distributed at four corners, wherein steel frame girders are arranged in the centers of the four steel frame columns; the steel frame columns and the steel frame girders are assembled and fixedly connected together through wall shelf units; and wall frame floor plate units are assembled and fixed on the wall frame units in a matched mode. The tube-in-tube structure for the reinforced concrete core tubes and the integrally-assembled space steel grids is simple in structure and convenient to mount, can be safely used, is stressed uniformly, has high assembly accuracy, and improves the construction progress.