Received signal processing and target reconstruction technique plays a key role in coherent field imaging, and directly influences the quality of the reconstructed image of a target. Based on all-phase fast Fourier transformation (FFT) spectrum analysis theory, a new processing and reconstruction method is proposed. By directly extracting the phase and amplitude information from all-phase FFT spectrum of the return signal, the proposed all-phase target reconstruction method is capable of inhibiting the frequency error caused by many factors, thus reconstructing the target image more precisely. The validity of the proposed method is proved by a coherent field imaging system in outdoor environments, and it has a better reconstruction performance than a traditional method. The resolution of the reconstructed target is close to a theoretical diffraction limit.