Due to an oil spill accident occurred in Taean coastal zone wide range of coastal waters were polluted. Inaccurate prediction of spilled oil trajectory is known as a cause that has increased the pollution damage in the beginning stage. In this study, a numerical modeling of spilled oil dispersion has been conducted to know which physical factors caused the severe and wide pollution. Especially the simulation is focused on how to model hydrodynamic circulation accurately. The simulation results showed that the hydrodynamic flow is very important in predicting oil fate, specially, in the short-term dispersion of spilled oil.