This study surveyed the sea level change concerned with paleoclimate based on the soil layer of foot at Mt. Osung located in the Geum River Estuary. We trenched two site with 2 ~ 3 meter deeps and collected samples. Samples were analyzed on the basis of sedimentary facies and grain size analysis. The research result shows that characteristics of grain size distribution is similar to intertidal sediments of Yellow sea, and sediments have the marine sponge spicules and glauconites which indicate a marine environment. The upper sediment layer is the finer of the grain size of the sediments(3.56φ~8.13φ) and the better of the roundness of grains. After last glacial age, transgressed sea level, this area had been submerged. And then, slowly regressed sea level, the gently sloped mountain foot of Osung-san had been remained.