Based on the daily reanalysis data of NECP/DOE, the persistent low temperature event in southern China in January 2016 is analyzed. The results show that this process has obvious characteristics of intraseasonal oscillation, and the Quasi-Biweekly Oscillation (QBWO) is the main mode of temperature change. The low temperature event reached the cold wave level because the synoptic scale change was in the same cooling process as the quasi-biweek oscillation of 10—20 d temperature. The quasi-biweekly scale cold center and synoptic scale cold center both propagate from mid-high latitudes to low latitudes and converge in the south of China, causing persistent low temperature. Through the diagnosis of the local variation equation of temperature, it is found that the temperature advection term and the adiabatic change term are the main reasons for the local temperature decrease in the near-surface layer in this synoptic process. The synoptic scale temperature change and 10—20 d low frequency oscillation both contribute greatly to the continuous cooling, and the contribution of the synoptic scale cooling is slightly bigger than that of the low frequency cooling.