Physicochemical characteristics of Kwangyang Bay, have been investigated on the effects of inputting rivers just after rainy season in summer 2003. The results ranged from 4.96～8.01 mg/L for DO, 1.16～3.09 mg/L for COD, 7.21～67.71 uM for DIN and 0.12～121.84 uM for phosphate. The COD of Yeosu Area was 1.19～3.09 mg/L, Kwangyang Area was 1.23～2.76 mg/L. The COD of Wallae cheon in Yeosu Area was 3.09 mg/L and Donghoan in Kwangyang Area was 2.76 mg/L. The reason of high COD might be industrial sewage of organic chemical plants and iron foundry. DIN of Yeosu Area and Kwangyang Area were 7.21～63.43 ${mu}M$ and 8.43～67.71 ${mu}M$ respectively. The average phosphate of Yeosu Area was 23.65 u. The source of phosphate might be industrial sewages of fertilizer plant and phosphate gypsum stocked with high amounts. The metal concentrations were measured in the range of 1.01～175.10 ${mu}g/L$ for Cu, 0.13～1.78 ${mu}g/L$ for Cd, 1.13～5.21 ${mu}g/L$ for Pb, 1.58～13.57 ${mu}g/L$ for Cr and 1.07～20.68 ${mu}g/L$ for As. The average Cu concentration was 78.99 ${mu}g/L$ in Kwangyang Area. The source of Cu might be industrial sewage of iron foundry. The average Cr concentration of Yeosu Area was 9.07 ${mu}g/L$. That is 2 times higher than Kwangyang Bay 5.74 ${mu}g/L$, because of sewage of chemical plants.