The invention relates to an adaptive structure, in particular to an interstage adaptive structure of a spacecraft. The interstage adaptive structure of the spacecraft comprises an upper end frame (1), a lower end frame (2), a supporting beam (5), an upper connector (3) and a lower connector (4). The supporting beam (5) is composed of one or more buckling beams (7), axial loads are applied to the buckling beam (7), the forked position of the buckling beam is subjected to bending deflection, and when the loads are close to critical buckling loads, a connecting screw (8), a negative-stiffness metal reed (9), a damping gasket (10) and a linear spring (12) are mounted at the transverse deformation position of the Euler's buckling beam (7). The interstage adaptive structure has the advantages of being high in longitudinal stiffness and large in transverse damping output, the requirement of the structure for high stiffness connection is met, the need for vibration reduction and isolation can be met through large transverse damping output, and the problem that the high stiffness and high damping of a traditional structure contradict each other and are incompatible is solved.