In order to evaluate the weed suppressing effect of Solanum viarum Dunal. In this study species diversity in patch of S. viarum and allelopathic effects of the aqueous extracts on S. viarum were investigated. Number of species and species diversity in site close to patch of S. viarum were decreased gradually 1site (7.7±2.0, 1.5±0.2), 2site (5.3±1.2, 1.2±0.2) and 3site (4.0±1.7, 0.9±0.1). And total phenolic compounds of soil in survey area were increased gradually site1 (0.16±0.01㎎ g⁻¹), site2 (0.17±0.01 ㎎ g⁻¹) and site3 (0.22±0.02㎎ g⁻¹). So the number of species and species diversity (r=-0.692, P＜0.05) were negatively correlated with increased total phenolic compounds of soil in the survey area. The relative germination ratio, the mean germination time, the relative elongation ratio, the fresh weight and the dry weight of receptor plants are generally getting decreased while the concentration of the aqueous extracts from S. viarum escalate. But every ratio was various depending on the growing regions, the kind of receptor plants and the treatment of the aqueous extracts. Especially, the radicle by injection of the aqueous extracts concentration of S. viarum was influenced more than the shoot on the same condition. The total phenolic compounds on region of S. viarum was gradually increased in stems (fresh 0.56±0.02㎎ g⁻¹, dry 1.58±0.08㎎ g⁻¹), roots (fresh 1.77±0.07㎎ g⁻¹, dry 2.64±0.06㎎ g⁻¹), leaves (fresh 6.01± 0.14㎎ g⁻¹, dry 7.04±0.29㎎ g⁻¹), seeds (fresh 6.21±0.17㎎ g⁻¹, dry 9.08±0.73㎎ g⁻¹) in order. On the contrary, the negative correlation on germination and growth of receptor plants was shown by total phenolic compounds on the each parts of S. viarum. We think that the aqueous extracts of S. viarum showed allelopathic effects on other plants. Therefore, S. viarum holds the higher competitiveness in plant community in Jeju Island and makes possibility of application as natural herbicide.