Here， we present our implementation of two-dimensional （2D） high-resolution inverse synthetic aperture radar （ISAR） imaging using a 0.22 THz stepped-frequency （SF） radar system. The system is suitable for both near- and far-field imaging with a synthesis bandwidth of 12 GHz. The radar can provide highly accurate range and cross-range results in the near field， and its ISAR image can reach centimeter-level resolution upon using a phase-compensated Back-Projection algorithm （BP algorithm）. These BP-realized results indicate that THz ISAR imaging can achieve both higher precision and finer resolution when compared to previously demonstrated range-doppler （RD） results with the same SFCW radar setup. To accelerate BP’s relatively slow image retrieval process， we employ accelerated platforms based on a graph-processing unit （GPU）. Such success should pave the way for further research on near-field high-resolution radar imaging especially at THz/sub-millimeter bands.