ver and seawater solutions diluted with the Changjiang River water at one atmoshpere from 5-35 salinity and 15-25℃ with a high precision magnetic float densimete designed by us. The average standared deviation of measurement values was ±2.3×10-3kg/m3. The stawtistical results have shown hat for all samples form the estuary of Chingjiang River, the measured density with our densimeter was always higher than the density calculatedby the UNESCO Equation, the average difference, for seawater samples taken in dryseason and flodseason, being (6.3±2.3)×10-3kg/m3 and (8.1±2.3)×10-3kg/m3, respectively. The average difference between the measured and calculated densitied in creasedwith decreasedsalinityand reached 47.2×10-3kg/m3 (Chanjiang River water). We have also found linear correlation relationships between this average diffrence and [Ca2+]/s value. Our experimental average valueof of [Ca2+]/s, [So2-]/s, [Mg2+]/s and [Sr2+]/s was 0.01183±1.0×10-4, 0.07698±17.×10-4, 0.03743±8.1×10-5 and 2.26×10-4, respectively, at the salinities of samplesrange form 30 to 35. The experimental value of [Ca2+]/s for the Wuhu section of Changjiang River was 0.2597. The resulting densities of all samples have benn fitted to an equation of the form: d-dw=B1S1/2+B2S+B3S3/2+ +B4S2, where dw is the denstiy of SMow and B1, B2, B3, B4, are temperature dependent parameters. The average standard deviation betweem calculated densities of this equation and experimatal value was ±3.9×10-3kg/m3.