The study on the water quality of the estuary of Seom Jin river and Gwang Yang bay was carried out for the purpose of environment survey of Gwang Yang bay on May, July, and September in 1974. Under the various atmospheric condition the sample were taken and analyzed by the 13 selected items of chemical and physical standard method. The results are as follow. Ⅰ. Estuary of Seom Jin river (St. 11). This area is greatly influenced by Seom Jin river in water quality and has fairly good and fresh like water quality. Flowing into Gwang Yang bay, this water has a dilution effect of pollution substance and salinity in bay. Ⅱ. North area of Myo island (St. 9, 10). This area is also affected by Seom Jin river but less than St. 11 and especially the chlorine ion content increase suddenly. Ⅲ. East area of Myo island (St. 4, 6). The fresh water of Seom Jin river and sea water out of bay, they equally affect this area, and has a little increasing tendency of pollution as compared with St. 9 and 10. Ⅳ. West area of Myo island (St. 7, 8). Tidal Current in this area is some what delayed on account of being interrupted its flowing by Myo island and there is not any higher polluted station in bay than in this station. Ⅴ. Enterance of bay (St. 1,2,3) and Nam Hae bridge(St.5). Being adjacent to the outer sea, those area are influenced by sea water and show nearly oceanic water quality. ⅥⅦ