Based on the monthly weather report of Korea Meteorological Administration (KMA) and daily sea surface temperature (SST) data from National Fisheries Research and Development Institute (NFRDl) (1991-2001), mean heat fluxes were estimated at the Gunsan harbor Net heat flux was transported from the air to the sea surface during March to early September, and it amounts to $125;Wm^{-2}$ in average daily during May to June. During the middle of September to February, the transfer of net heat flux was conversed from the sea surface to the air with $-125;Wm^{-2}$ in mininum value in October. Short wave radiation was ranged from 50 to $248;Wm^{-2}$ showing maxima in April to June. Long wave radiation was ranged from 25 to $92;Wm^{-2}$ with mininum value in June to July. Sensible heat flux denoting negative values in April to August was ranged from -30 to $72;Wm^{-2}.$ Latent heat flux was ranged from 15 to $82;Wm^{-2}$ with maxima in August to September. The phase of heat exchange was changed from cooling to heating in the end of February, and from heating to cooling In the beginning of September. The advective term of heat flux showed minima in April to June and maxima in November. The ratio of temperature variations was 1.37 in the sea surface process and the horizontal process by advection. This indicates that the main factor in variation of temperature at Gunsan harbor is the heat exchange process through the sea surface from the air.