According to the oceanic investigations, we have performed in the expedition from June to October, 1935, we see that the salinity at surface in Gulf of Pechihli is the lowest at the mouth of Yellow River, where the mean value of five months from June to October is below 26.5‰. Northeastward from here till Strait of Tengchow (Strait of Pechihli) the salinity increases from 25.5 to 30.7‰, there-fore the gradient is rather steep (ChartⅠ.), At the mouth of Lwon-ho the salinity is also lower than that of middle part of the gulf, but the influence is naturally not so prominent as that of Yellow River.