Noni (Morinda citrifolia L.) is an edible and medicinal fruit distributed in Tirunelveli, India. The antibacterial activities of the extracts of water, petroleum ether, ethyl acetate, chloroform, and n-butanol were assayed by the disk diffusion method. The results showed that the extracts from Noni fruit possessed antibacterial effects against Bacillus subtilis, Escherichia coli, Proteus vulgaris, and Staphylococcus aureus. Among 5 different extracts, the Butanol extraxt produced the best antibacterial activity. The samples were first extracted by ethanol, and the primary compounds in the fraction of ethanol extract Butanol extraxt was further isolated and identified. Six phenolic compounds, including 5, 15-dimethylmorindol, ferulic acid, p-hydroxycinamic acid, methyl 4-hydroxybenzoate, methyl ferulate, and methyl 4-hydroxycinnamate, were identifiedby NMR. The results indicated that the phenolic compounds might significantly contribute to antibacterial activities of Noni fruit.