This research focuses on the discussion of climate abrupt change and instability for millennial and centennial scale in the early and middle Holocene (11. 5 - 3. 5KaB. P.) based on a comprehensive analysis of grain size,magnetic susceptibility,geochemical parameters and chronology in the Pingliang Dazhai loess section. It indicates that the YD event appeared in the early Holocene (11. 5 - 9. 2KaB. P.) which reflects the climate reversal. Climatic deterioration (6. 5 - 4. 5KaB. P.) during the Megathermal(9. 2 ~ 3. 5KaB. P.) included two several centennial - scale cold and dry climate events. The climate and environment deterioration during the extreme cold and dry climate events were almost close to the late glacial. Moreover,the period of climate change cycle during the mid - Holocene in the area was about 1. 5ka.