The invention discloses a SAR differential tomography method and device. An iron tower is observed by using a radar to obtain an original echo of a tower SAR; distance and azimuth compression is carried out on the original echo to obtain observation matrixes on a plurality of SAR images; the observation matrixes are decomposed into a height matrix and a deformation velocity matrix; on the basis ofa two-dimensional sparse reconstruction algorithm, two-dimensional information sparse reconstruction is carried out on the height matrix and the deformation velocity matrix respectively to obtain a reconstructed height matrix and a reconstructed deformation velocity matrix; and strong scattering point information of the tower is obtained based on the reconstructed height matrix and the reconstructed deformation velocity matrix. According to the invention, the original echo of the tower SAR is processed, the height matrix and the deformation speed matrix are reconstructed by combining the two-dimensional sparse reconstruction algorithm, and then the strong scattering point information of the tower is obtained. Therefore, a problem of the large computing load for the iron tower height and deformation rate extraction in the prior art is solved; and the practical progress of the satellite remote sensing technology in the transmission line tower deformation monitoring is promoted.