Abstract: In memory of the excellent contributions made by academician Tao Shiyan to the study on East Asian winter monsoon (EAWM), the characteristics and internal dynamical causes of winter surface air temperature in China and the EAWM occurring near the late 1990s are analyzed in this paper by using observational data in China and reanalysis data of the NCEP/NCAR and ERA-40/ERA-Interim. The analyzed results show a significant jump of interdecadal variability of winter surface-air temperature in China and the EAWM occurrence in the late 1990s. With the strengthening of the EAWM, this variability of winter surface air-temperature in China has undergone a change from a "similar pattern in the whole China" to a "south-north oscillation pattern" (i.e., cold in the north but warm in the south) since 1999. Because the winter surface-air temperature in northern China shifted into a colder state during 1999-2012, wintertime disasters of low temperature, snowstorms, and blizzards have frequently occurred in this region. In addition, the dominant period of the interannual variability of winter surface-air temperature and the EAWM turned into 2-8 years from previous 3-4 years. Moreover, the results show that this interdecadal jump of the EAWM is attributed to the strengthening of the Siberian high and the Aleutian low. The internal dynamical causes and physical mechanism of this interdecadal variability of the EAWM are discussed further from the dynamical theories of Arctic Oscillation (AO) and quasi-stationary planetary wave activity. Since the late 1990s, the propagation of quasi-stationary planetary waves into the stratosphere over high latitudes of the Northern Hemisphere along the polar wave-guide was enhanced, while the propagation into the upper troposphere over the subtropics along the low-latitude wave-guide weakened, which caused the strengthening of the convergence of Eliassen-Palm (E-P) fluxes of quasi-stationary planetary waves in the troposphere and stratosphere over high latitudes and strengthening of the divergence of E-P fluxes in the middle and upper troposphere over the subtropics of the Northern Hemisphere. This led to the weakening of wintertime zonal-mean zonal flow from the troposphere to the stratosphere over high latitudes of the Northern Hemisphere and the polar front jet and strengthening of the wintertime subtropical jet during 1999-2012, which caused the weakening of the wintertime AO and strengthening of the EAWM.