MODIS/Terra level 3 and NCEP/NCAR Reanalysis data from 2001 to 2008 have been analyzed to understand long-term aerosol and cloud optical properties, and their relationships around Korea. Interestingly, cloud fraction(CF) has the similar annual variation to aerosol optical depth (${ au}_a$) without any temporal significant trend. Horizontal distributions of ${ au}_a$ showed the substantial horizontal gradient from China to Korea, especially with the strong difference over the Yellow Sea, which could represent the evidence of the anthropogenic influence from China in the perspective of long-term average. Specifically the negative correlations between ${ au}_a$ and liquid-phase cloud effective radius ($r_e$) were shown on the monthly-average basis, only in summer with significant associations over the Yellow Sea, but not in the other seasons and/or specific regions. Relationship between ${ au}_a$ and CF for the low-level liquid-phase clouds exhibited the overall positive correlation, being consistent with cloud lifetime effect. Meanwhile static stability showed no deterministic relationships with ${ au}_a$ as well as CF. The dependence of aerosol-cloud relationship on the meteorological conditions should be examined more in detail with the satellite remote sensing and reanalysis data.