This study describes the improved calibration applied for VIIRS SDR reprocessing. At reflective solar bands (RSBs), the earth-view F-factor is adjusted with the lunar observations and changes about 2% in band M2-M4 in past five years. An empirical method is applied to remove the radiance spikes in VIIRS thermal emissive bands (TEBs) during the blackbody Warm-Up-Cool-Down (WUCD). VIIRS DNB calibration is improved by applying continuous spectral response changes, new bias tables, updated gain ratio tables, stray light tables, and terrain corrections.