Seasonal and secular variations of water temperature in Chungmu port were investigated with the data obtained from the Technical Reports(1976~1983) of Hydrographic Office. Monthly and annual range of water temperature were 2 to 8$^{circ}C$ and 18 to 21$^{circ}C$, respectively. The coefficients of variance of monthly mean water temperature were 0.015(February, 1976) to 0.208(December, 1980) and their values were smaller in the summer season than in the winter season. The result of harmonic analysis for investigating the seasonal variation of water temperature was T(t)=15.66+8.06 cos(10$^{circ}$t-233.5)+0.92 cos(20$^{circ}$t-216). The periods of secular variation were about 2 years and 3 years.