The invention, which belongs to the technical field of the GIS mechanical fault vibration monitoring, provides a detection system and method for GIS mechanical fault vibration. The system comprises an acceleration sensor, a signal processing unit, a signal acquisition unit and an upper computer, wherein the above-mentioned units are installed in a GIS housing. An operation state of a GIS device is determined based on a frequency spectrum of a vibration signal and thus the working state of the totally-enclosed power system switch can be determined at first time, so that the system and method have an important significance in secure operation and reliable power supply of the power system. The upper computer can determine whether a received signal is a vibration signal of a GIS device housing automatically and process a low-frequency interference signal automatically,, thereby guaranteeing the work efficiency of the detection system. GIS devices that have different voltage levels and are from different sound field manufacturers in the power system have different housing vibration spectral characteristics; and thus adaptation to detection of various application environments is guaranteed based on comprehensive database recourses.