|In order to assess the water quality of Kumho river using Diatom Assemblage Index to organic water pollution (DAIpo) and to campare from the previous water quality, 5 sites in Kumho river were selected and assessed total of 6 times, every April and September from April 2010 to September 2012. As a result, 116 taxa were found in 2 Order, 3 Suborder, 7 Families, 26 Genera, 103 species and 13 varieties. Saprophilous species of 10 dominant species including Achnanthes minutissima, were increased as going to downstream sites. Correlation coefficients (r) between epilithic diatom communities and physicochemical factors were from - 0.62 to 0.71. Correlation coefficients (r) between TN and diatom indices (DAIpo, TDI) were 0.57 and 0.65, respectively. Therefore, epilithic diatom communities were greatly influenced by TN. The Correlation between DAIpo and TDI measured to be high in correlation coefficient (r=0.62) from the result of correlation analysis. Mean of DAIpo values ranged between 37.24~ 74.98 and decreased as going to downstream sites. Saprobic level was estimated as β-oligosaprobic at st. 1, α-oligosaprobic at st. 2 and β-mesosaprobic at st. 3. But st. 4 and 5 which were α-mesosaprobic and polysaprobic in the previous results, were improved as β-mesosaprobic. The RPId, general assessment of the water quality using DAIpo, was 52.27, which means the water quality of Kumho river was middle level.