The utility model discloses a GIS fault diagnosis system based on vibration signal spectral analysis, and belongs to the field of GIS faults monitoring. The system comprises vibration acceleration transducers, a charge amplifier, a data acquisition instrument, and a PC machine connected in series in sequence, and the vibration acceleration transducers comprise three vibration sensors respectively fixed on an X, Y, and Z axis directions on an outer surface of a GIS box. The system utilizes the three vibration sensors to collect GIS vibration signals on the X, Y, and Z axis directions, the vibration signals are preprocessed, spectral analysis is carried out, energy of characteristic frequency is calculated, the calculated value is compared with normal state, and according to compare results and threshold value, the GIS faults are determined. The GIS fault diagnosis system based on vibration signal spectral analysis is easy in engineering realization, accurate in diagnosis, and high in reliability.