Keeping oscillation of low frequency of 30~60 days, Butterworth band-pass filter method was used to process the NCEP/NCAR reanalysis data. Based on the application of the low-frequency synoptic map, low frequency features of the two extreme low temperature events were analyzed in order to reveal the characteristics of the low frequency systems during these two events. The results show that in early 2008, large-scale atmospheric systems including blocking-high and upper-level jet stream all featured a distinct 30-60-day oscillation. The positive (negative) anomaly of geopotential height was closely coincided with the low frequency high (low) pressure of the low frequency systems, and the center of positive zonal wind anomaly was consistent with the high value center of low frequency zonal wind. Meanwhile, the positive phase of the AO favored the strengthening of the Middle East jet and the maintenance of the blocking high, resulting in durative low temperature in south China. The 30-60-day oscillation features of the weather systems including upper-level jet and blocking high were not so obvious during “overlord”-level cold wave in 2016. However, the low pressure of low frequency can describe the generating and developing of the polar vortex. Under north air stream at the front of blocking high ridge guidance, the rapid invasion of strong cold air in the middle of polar vortex caused temperature in China drop fast. The low-frequency synoptic map reflected the phase transition of AO before and after the cold wave. The phase of AO was positive in later December 2015 while negative in early January 2016. Then the polar cold air invaded southern China, which can be conclude as the main cause of the sharp drop in temperature. The low-frequency flow field showed the phase transition of AO lagging behind the synoptic flow field about two days during the two events.