Abstract: In order to ensure the seismic safety of freestanding equipment in isolated buildings, the freestanding equipment is simplified as a two-dimensional rectangular rigid body with rocking only, and the interaction between the freestanding equipment and the isolated structure is considered. The equations of motion of the isolated structure-overturned freestanding equipment combination system and the Simulink dynamic simulation model are established, and the maximum sway angle of the freestanding equipment in the isolated structure is obtained analytically under horizontal seismic action. The floor rocking spectrum of the isolated structure is defined as a dimensionless curve of the relationship between the maximum sway angle of the equipment and the period of the equipment, and then the statistical regression analysis method is adopted to fit and calibrate a large number of floor rocking spectra of the isolated structure in segments and obtain the floor design rocking spectrum of the isolated structure. Based on the real-time hybrid test method, a real test is carried out on the combined system of isolated structure and overturning-type of freestanding equipment, and the mean floor rocking spectrum of the isolated structure is plotted with the measured results and compared with the proposed floor design rocking spectrum of the isolated structure, and the results show that the proposed floor design rocking spectrum can objectively depict the main features of the floor rocking spectrum, and restore the curve variation of the spectrum. The two spectra are basically consistent with each other, and the average error of the spectral values at each periodic point is less than 5%, which indicates that the proposed floor design rocking spectrum is accurate and reliable. With this floor design rocking spectrum, for the overturning-type of cabinet freestanding equipment, as long as the equipment appearance size, equipment mass, seismic isolation structure parameters and earthquake parameters are known, the maximum sway angle of the freestanding equipment can be determined, which is convenient for engineering applications.