This study is based on comparative analysis of nLw(λ) and chlorophyll a retrievals in the Korean Sea from Kompsat-1 OSMI and SeaWiFS. The chlorophyll concentration from the SeaWiFS was 1.6 times higher than that from Kompsat-1 OSMI during the period. Comparison of Level-2 data indicates that nLw of OSMI was about 10 times higher than that of SeaWiFS in the Korean Sea. In sea area, nLw(555) value has a large differences, however, the coefficient of determination shows the high relationship as 0.97. There are some possible causes for such discrepancy: differences in the sensor sensitivity, radiance calibration, atmospheric correction algorithm, and influence of OSMI stripping. We examined some of these possibilities. The deviation between the two data sets was highly correlated with nL w(555). Therefore, the atmospheric correction, radiance calibration and stripping of OSMI seem to be the major cause of the discrepancy.