To know the ratio of the Northwestern Pacific Water in the Tsushima Current, CTD data observed in 2008 and 2010 were analized. Based on T-S diagram, 4 water masses were identified: East China Sea surface water, Yellow Sea Bottom Cold Water, North Pacific Under Water, and North Pacific central water. Water mass ratios were analyzed in the south sea section with these water masses. This results suggest that the high salinity water in the south sea is originate from the water below Kuroshio high salinity water. North Pacific Under Water, and North Pacific central water. Water mass ratios were analyzed in the south sea section with these water masses. This results suggest that the high salinity water in the south sea is originate from the water below Kuroshio high salinity water.