The narrow sense and applicable limit of Practical Salinity Scale 1978 (PSS78) and volumetric titration using silver nitrate to measure the salinity of non conservative oceanwater are discussed.The salinity obtained by electrical conductivity method and chlorinity salinity method obviously deviates from the absolute salinity( S A). The Density Salinity Scale(DSS98)proposed by the writers can be extensively used in conservative and non conservative water samples. The merits of the density salinity scale are as follows. (1)The Density Salinity Scale is only related to seawater mass and its buoyant effect, and is not influenced by the variation in seawater composition, and therefore,has high reliability,and repeatability for salinity determination. (2)The salinity values measured by the DSS98 have a conservative property.For oceanwater samples the salinity values are the same as those determined by the PSS78; for non conservative water samples(e g. samples from industrial sources),the salinity values are close to the absolute salinity values in comparison with those measured by the PSS78 and the Knudsen method. (3)For a solution with given solute mass,the solution concentration can be converted into the corresponding salinity by the Density Salinity Scale using the expansion coefficient of the solution and the calibration coefficient of the partial molar volume of the solute. The narrow sense and applicable limit of Practical Salinity Scale 1978 (PSS78) and volumetric titration using silver nitrate to measure the salinity of non conservative water are discussed. Salinity obtained by electrical conductivity method and chlorinity salinity method obviously deviates from the absolute salinity (SA The Density Salinity Scale (DSS98) proposed by the writers can be extensively used in conservative and non conservative water samples. The merits of the density salinity scale are as follows. (1) The Density Salinity Scale is only related to seawater mass and its buoyant effect, and is not influenced by the variation in seawater composition, and therefore, has high reliability, and repeatability for salinity determination. (2) The salinity values ​​measured by the DSS98 have a conservative property. For oceanwater samples the salinity values ​​are the same as those determined by the PSS78; for non conservative water samples (e g. samples from industrial sourc es), the salinity values ​​are close to the absolute salinity values ​​in comparison with those measured by the PSS78 and the Knudsen method. (3) For a solution with given solute mass, the solution concentration can be converted into the corresponding salinity by the Density Salinity Scale using the expansion coefficient of the solution and the calibration coefficient of the partial molar volume of the solute.