The study results of the water param~ters in the Cua Sot and Cua Khau rivermouths (Ha Tinh province) during dry season 2002 are as following: The average concentration of the parameters in Cua Sot during the high tide included: salinity 27. 7ppt, N-NO3 17.4 pg/l, NO2 0.61 ug/l, P-PO./ 7.4 ug/l, NNH./ 2.3 pg/l, DO 4. 61ml/l, Chi-a 3.13 ug/l, BOD5 0.48 mg/l and Coliform 23.6 cells/ml. During the low tide were salinity 28.6 ppt, N-NO3 12.3 ug/l, N-NO2 0.84 pg/l, P-PO./ 15.0 pg/l, N-NH./ 3.6 ug/l, DO 4. 61ml/l, Chi-a 3.13 ug/l, BOD5 0.48 mg/l and Coliform 7.7 cells/ml. Their average concentrations in Cua Khau during the high tide were salinity 19.0 ppt, N-NO3 52.8 ug/l, N-NO2 0.65 ug/l, PO/ 9.0 ug/l, N-NH/ 7.1 ug/l, DO 5.08 ml/l, Chi-a 3.34 ug/l, BOD5 0.50 mg/l, Coliform 19.8 cells/ml. And during the low tide salinity 13.-1 ppt, N-NO3 74.0 pg/l, NO 0.90 pg/l, P-PO4 6.1 pg/l, N-NH,7.5 pg/l, DO -1.93 ml/l, Chl-a 2.72 pg/l, BOD5 0.58 mg/l and Coliform 20.0 cells/ml. Most of the parameters in Cua Sot and Cua Khau are low. It showed that environment in these areas had been not polluted by organic matters.