Circulation in the East Asian Marginal Seas (EAMS) were investigated using an ocean general circulation model (OGCM). The OGCM is based on the GFDL MOM3. Model domain is expanded to the whole North Pacific Ocean (100E-70W and 20S-66N) to get the natural lateral boundary conditions for the EAMS. Horizontal resolution is increased from 1 degree to 1/6 degree toward the EAMS region. For the initial condition World Ocean Atlas (WOA) 2001 annual mean temperature and salinity were used. Monthly-mean wind stress forcing was applied using ECMWF wind stress. A restoring condition was adopted using WOA2001 sea surface temperature and salinity for the surface thermohaline forcing. Several different cases were run; topography adjustment, wind stress refinement, and thermal forcing adjustment. The control run (no adjustment case) showed a strong warming both in the Yellow Sea and the East/Japan Sea with an overshooting of the East Korean Warm Current. When combined with the topographic adjustment and wind stress refinement, the thermally adjusted case showed an improved circulation pattern; a better reproduction of temperature distribution and a realistic current pattern in the EAMS.