Abstract: Salinity vertical distribution and salt-fresh water mixing process were summarized by sorting out and analyzing salinity data synchronously observed at eight estuaries of the Pearl River during the dry season of 2016. The results showed that due to the differences in hydrodynamic conditions at the eight estuaries and the direction of each estuary, the invasion intensity of salt water and the mixing degree of salt and fresh water at each estuaries showed differences in time and space distribution. The salinity distribution is characterized by a gradual increase to both east and west directions, with Hengmen as the center. On the whole, the stratification parameter was the minimum at Hengmen and decreases gradually with Hengmen as the center to the east and west. In a tidal cycle, the intrusion degree of salt water and the mixing strength of salt and fresh water showed periodic characteristics with the ebb and flow of the tide. Salinity gradually increases from the top to the bottom and there exists a point where salinity changes rapidly in the vertical direction. Generally, the stronger the tidal force is, the higher the position of this point will be for the eight estuaries, the highest position of that point is oberserved at Humen and Yamen, and the lowest at Jiaomen, Hongqili and Hengmen.