Abstract: In this paper, we designed a critical index |v/u| to determine the exists and the evolutional characteristics of the equatorial westerlies by using the FGGE data from May to August of 1979.The structures of the equatorial westerlies and its relationship with the large-scale circulation in the low latitudes is discussed in details. It shows that these equatorial westerlies are an important basic current in the low latitudes in Indian Ocean. Finally, the schematic picture of the three-dimensional circulation structure of these equatorial westerlies as given.