A novel Synthetic aperture radar(SAR)signal processing technique has been proposed which refocused slow moving targets based on phase retrieval algorithm. After theoretical derivation, we can get that the raw data Fourier magnitude of slow moving targets is approximate to the stationary ones in the SAR system. By applying the Fourier magnitude of received data to phase retrieval algorithms, the blur and defocusing effect caused by the moving of the targets can be eliminated. The simulated results demonstrate the validity of this algorithm. A novel Synthetic aperture radar (SAR) signal processing technique has been proposed which refocused slow moving targets based on phase retrieval algorithm. We can get that the raw data Fourier magnitude of slow moving targets is approximate to the stationary ones in the SAR system. By applying the Fourier magnitude of data to phase retrieval algorithms, the blur and defocusing effect caused by the moving of the targets can be eliminated. The simulated results demonstrate the validity of this algorithm.