Phytotoxicity, antioxidant activity, and cytotoxicity of the aqueous or methanol extracts from the young sprouts of the six Compositae medicinal plants were determined. Aqueous leachates at 40g dry tissue $L^{-1}$ (g $L^{-1}$) Cirsium japonicum and Aster yomena showed the highest inhibitory effect on alfalfa (Medicago sativa L.). Total phenolic content showed the highest amount in methanol extracts from Ixeris dentata, and followed by A. yomena, and Cephalonoplos segetum. Methanol extracts of C. segetum and I. dentata at 25${mu}g$ m$L^{-1}$ exhibited the highest DPPH radical scavenging activity by 87.2, and 52.8%, respectively. By means of HPLC analysis, MeOH extracts of C. segetum had the highest amount of antioxidant chlorogenic acid. Based on MTT assay, the methanol extracts from Y. sonchifolia ($IC_{50}$ = 65.7${mu}g$ $mL^{-1}$) showed the highest cytotoxicity against Calu-6. These results suggest that plant extracts had a dose-dependent biological potentials including phytotoxicity, antioxidant activity, and anticancer activity, and that their activities exhibited differently depending on plant species.