Five caffeoylquinic acids of Aster altaicus var. uchiyamae Kitamura (Compositae) leaves were identified using standard compounds by HPLC and determined as follows: 3,4-di-O-caffeoylquinic acid (4.92 ± 0.06 ㎎/g dried weight), 3,5-di-O-caffeoylquinic acid (3.95 ± 0.13 ㎎/g), 4,5-di-O-caffeoylquinic acid (1.39 ± 0.10 ㎎/g), 5-O-caffeoylquinic acid (chlorogenic acid, 8.05 ± 0.21 ㎎/g), 3-O-caffeoylquinic acid (4.97 ± 0.18 ㎎/g). The total content of five caffeoylquinic acids were calculated as 26.73 ± 0.26 ㎎/g dried weight while the percentage of the five compounds in the MeOH extract was calculated as 25.22 ± 0.25%. The IC50 value of the MeOH extract scavenging peroxynitrite (ONOO - ) was shown as 5.16 ± 0.15 ㎍/㎖.