The precipitation data from the Korean ancient instrument, Chukwookee, provides the longest daily precipitation for studying the multi-decadal to centennial variability and trends in Seoul summer precipitation. Recently, Wang et al. (2007) analyzed the characteristics of the variability and singularity in this precipitation data. They found that the Korean rainy season has been considerable changes in multidecadal-centennial scales during the 1778-2004. The date for peak rain intensity during the rainy season shows a multi-decadal oscillation. In addition, Korean Peninsula shares the characteristics of the intraseasonal variations of summer-precipitation with East Asia including East China and Japan. This study considers the long-term variability of the East Asian summer monsoon associated with long-term variations of Seoul precipitation using CRU (Climate Research Unit) precipitation dataset which is based on station data and covers only land area.