Inverse Synthetic Aperture Imaging LADAR can realize the instantaneous high-resolution imaging for moving target. Howerver, the ultra-wide bandwidth of the laser signal and the weakness of the echo signal brings some difficulties in the signal sampling. A method which combines the optical heterodyne detection technique and compressed sensing theory is proposed to solve this problem. The optical heterodyne detection technique is utilized to reduce the bandwidth of echo signal, then the compressed sensing theory is developed to realize sampling and reconstruction of the signal. Simulations demonstrate that high-quality images can be reconstructed even though the sampling rate is much lower than the Nyquist rate.