The study mainly focuses on the seasonal variation of mass transport in the Eastern Indian Ocean (EIO) using ECCO2 model simulation data covering 20 yr period of 1992-2012.Three sections are selected at the equator,80°E,and 6°N in the EIO.The study reveals that the major seasonal transport across the equator and 80°E are roughly compensated.Most of the mass transport across the equator is confined to the upper 100 m,whereas that across 80°E it has complex structure associated with prominent monsoon currents,WJs,EUC and so on.Although the net upper mass transport across 6°N is small,there are strong boundary current and relatively weak interior currents.Significant changes of zonal current occur at 80°E.During the prevailing monsoon season,mass transport near the equator is dominated by westward gradient current due to WJs relaxation,while monsoon current dominates the rest region in the upper 100 m.Similarly,there is transition between westward gradient current due to EUC relaxation and eastward EUC for subsurface layer.During transition seasons,monsoon currents weaken.Instead,WJs and EUC dominate in upper 100 m and subsurface layer,respectively.Besides,the saline and warm water exchanges are discussed associated with monsoon currents,WJs,and EUC,which is helpful to understand both horizontal and vertical structures of temperature and salinity in the study domain.