In this paper, high-resolution 3-D radar imaging using a 3-step image formation procedure based on the Huggens-Fresnel's principle is analyzed and discussed. To achieve high spatial resolution, large antenna array is required. The array can be implemented with a synthesized antenna array, or a sparse antenna array. To achieve high range resolution, pseudo-random noise (PN) coded signal waveform is used. The ability of generating high-resolution 3-D imaging is verified by computer simulation. Numerical simulation shows the reconstructed 3-D radar image of an object. PN coded signal waveforms also has the advantage of noise immunity. Applications of the high resolution 3-D radar imaging can be in ground penetration radars, microwave medical imaging, and down-looking SARs.