Based on the weekly snow cover data in the Northern Hemisphere from Jan.1,1973 to Dec.31,2000 provided by NOAA-NESDIS,the spatial/temporal characteristics of winter snow cover anomaly over Eurasia are studied.It is found that the perpetual snow of mid-high latitudes in Eurasia has obvious whole-distributing feature,while the winter perpetual snow south of 50°N varies with latitudes;the first EOF eigenvector of the inter-annual departure field of winter snow area over Eurasia indicates that the winter perpetual snow of mid-high latitudes exhibits an east-west opposite-phase distribution.Using wavelet analysis,time coefficients of the first and second spatial patterns of EOF analysis are analyzed,and it is found that the 3~4-year fluctuation period is the largest component in the temporal variation of Eurasian winter perpetual snow.Analysis indicates that the thermal anomaly of underlying surface brought about by Eurasian perpetual snow anomalies may possibly offer a triggering mechanism for the outbreak of El Nino in the next year.