Based on NCEP-DOE AMIP-Ⅱ (National Centers for Environmental Prediction, U.S. Department of Energy, Atmospheric Model Intercomparison Project Ⅱ) daily reanalysis data, a typical case of Anticyclonic Wave Breaking (AWB) that occurred on 20 December 2010 in the North Pacific region and the characteristics of Isentropic Potential Vorticity (IPV) during this process were studied. Daily high-frequency eddies and low-frequency variabilities were investigated. In addition, research was conducted on the modes of high-frequency eddies and low-frequency variabilities through Empirical Orthogonal Function (EOF) method on 350 K isentropic surface in the winter of 2010. Budget analysis of the IPV was employed to examine the low-frequency and high frequency PV anomalies associated with the primary modes of EOF. The results show that during the process of the Rossby wave breaking, low PV air parcels that emerged over the Northwest Pacific near Japan traveled to the upper troposphere, while high PV air parcels invaded lower troposphere. The first two leading modes of high-frequency PV depict a middle-latitude wave train that propagated from west to east over the North Pacific. The first leading mode of the low-frequency PV spread in the North Pacific as an arched wave train. The track of synoptic waves could be altered by the low-frequency variability, causing the waves to break eventually; meanwhile, the advection of high-frequency flows contributed to the conversion of the primary mode from high-frequency variability to low-frequency variability in the winter.