In order to investigate the influence of sea condition on the catch fluctuation of long line for common octopus, octopus variabilis, the oceanographic factors, i. e., the water temperature, the salinity and the density in the coastal waters of Yosu from Jan. 11 to Jul. 25 in 1997, and compared with the catches of common octopus, octopus variabilis by long line. The results obtained summerized as follows; 1) The range of water temperature, salinity and density from Jan. to Jul. at the sea area were 4.1~$23.6^{circ}C$, 31.7~34.5$ extperthousand$ and 21.30~27.81, respectively, and the catch of common octopus, octopus variabilis was high respectively at the temperature of 17~$-20^{circ}C$, at the salinity of 33.0~33.5$ extperthousand$ and at the density of $sigma$t 22.5~24.0. 2) The catch of common octopus, octopus variabilis was lowest from Jan. to Feb. and highest from May to June.