Abstract: The present study investigates ENSO impact on the variability of wintertime synoptic-scale air temperature over China based on daily averaged air temperature data collected at 753 stations and compiled by the National Meteorological Information Center, the NOAA reconstructed monthly sea surface temperature and the NCEP/NCAR reanalysis data from 1960 to 2017. The results show that ENSO is significantly positively correlated with wintertime synoptic-scale air temperature variability in a large area of eastern China. The fluctuation of temperature and synoptic-scale air temperature variability are usually stronger than normal during El Niño winters. In contrast, the synoptic-scale air temperature variability is weakened during La Niña winters. Further research finds that during El Niño winters, the meridional temperature gradient in the middle and high latitudes of Eurasia strengthens, leading to enhanced local atmospheric baroclinicity according to the thermal wind relationship and thus further increasing storm activities in the Siberian region and synoptic-scale variation of atmospheric circulation in East Asia region. Correspondingly, the synoptic-scale air temperature variability enhances in most areas of China. Roughly opposite mechanisms apply during La Niña winters.