The seasonal variation of the cross-equatorial flow in the eastern hemisphereis analyzed by using the 6-level monthly mean wind data from January 1979 to December 1987. The results are shown as follows:The center of the cross-equatorial flow exists in the lower troposphere in winter and summer but in the upper troposphere inspring and fall. The flow propagates southward in winter and fall but northward in summer and spring. The flow turns south wind into north wind in March and November inthe lower troposphere but in June and January in the upper troposphere. Remarkableanomaly is observed in the crossequatorial flow during the the El Nino year,but assumesdifferent forms. During the El Nino year, the summer lower cross-equatorial flow becomes steadily set up 2-3 pentads later than during the normal year and has more intraseasonal variation and shorter steay maintenance.