Presented at the 2014 Ocean Sciences MeetingBased on the Argo floats data, the low frequency salinity variability of the South Pacific Tropical Water (SPTW) is investigated in this study. Subsurface salinity along the 24.5 σθ surface in the South Pacific subtropical gyre exhibits a trend with dipole-like structure during 2004-2012. The northern side of the SPTW gets fresher by 0.3 psu, while the southern side gets saltier by 0.2 psu, suggesting a poleward shift of the water mass. Salinity along the SPTW core shows a relatively weak interannual variability with a peak-to-peak amplitude of 0.05 psu. Such a subsurface salinity variability seems to be connected with the sea surface salinity variability in the SPTW formation region, and the dipole-like structure of the salinity trend is further linked to the decadal variability of the evaporation minus precipitation in this region.