The invention relates to a three-dimensional image reconstruction method and device based on synthetic aperture radar imaging. The method comprises the steps of: using an emission signal of an antenna as a local oscillator signal, carrying out de-chirping processing on a collected original echo signal reflected back by scanned target, and obtaining a first intermediate signal; eliminating a residual video phase in the first intermediate signal, obtaining a second intermediate signal, carrying out Fourier transformation successively in height and orientation on the second intermediate signal, and obtaining a third intermediate signal; and carrying out inverse non-uniform rapid Fourier transformation on the third intermediate signal, and obtaining a three-dimensional image of the scanned target. By adopting the method, the time required by three-dimensional image reconstruction is shortened, and the precision of the reconstructed image is simultaneously improved.