Seventeen 30% EtOH extracts from the Compositae plants collected in Gangwon-do, Korea during autumn season were analyzed by HPLC using three standard caffeoylquinic acids (chlorogenic acid, 3,5-di-O-caffeoylquinic acid, 3,5-di-Omuco-quinic acid) and six flavonoids (rutin, isoquercitrin, astragalin, quercitrin, quercetin and kaempferol) to find the composition of phenolic compounds and also assayed to evaluate the peroxynitrite (ONOO$^-$) scavenging effect. The extracts with $IC_{50}$ values less than 2.0 ${mu}g/ml$ were as follows: Aster tartaricus ($IC_{50}$, $1.26{pm}0.10;{mu}g/ml$), A. maaki ($1.45{pm}0.03;{mu}g/ml$), Solidago virga-aurea, ($1.45{pm}0.03;{mu}g/ml$), Picris hierraciodes var. glabrescens ($1.45{pm}0.04 ;{mu}g/ml$), Lactuca triangulata ($1.50{pm}0.09;{mu}g/ml$), Chrysanthemum zawadskii ssp. acutilobum, ($1.79{pm}0.14;{mu}g/ml$). Particularly, the proportion of total phenolic compounds measured in the extract of L. triangulata was highest as the value 54.51%.