With the advancement of millimeter-wave radar technology, Synthetic Aperture Radar (SAR) imaging at millimeter-wave frequencies has gained significant attention in both academic research and industrial applications. However, traditional SAR imaging algorithms primarily focus on extracting two-dimensional information from detected targets, which limits their potential for 3D scene reconstruction. In this work, we demonstrated a fast time-domain reconstruction algorithm for achieving high-resolution 3D radar imaging at millimeter-wave (mmWave) frequencies. This approach leverages a combination of virtual Multiple Input Multiple Output (MIMO) Frequency Modulated Continuous Wave (FMCW) radar with the precision of Synthetic Aperture Radar (SAR) technique, setting the stage for a new era of advanced radar imaging applications.