We propose a distributed optical fiber vibration sensing scheme based on space difference interference of Rayleigh backscattering, to detect the swing of the optical fiber composite overhead ground wire (OPGW) over large areas. In this scheme, Rayleigh backscattered light with phase changes induced by the swing of the OPGW is split and fed into an imbalanced Michelson interferometer. We use the arm length difference of the interferometer to realize the Rayleigh backscattered light interference of adjacent space segments along the sensing fiber. The phase information is demodulated via 3×3 coupler demodulation technology, and the accurate measurement of the vibration signal is realized. We achieve the swing at 0.9 Hz and non-swing at 2.3 Hz in the transmission line swing laboratory.