Objective To study the chemical constituents of the herb of Ludwigia octovalvis. Method Chemical constituents were isolated by the repeated silica gel column chromatography, and their structures were elucidated by the physicochemical properties and spectral analysis. Result Thirteen compounds were obtained and determined as follows: beta-sitosterol (1), oleanolic acid (2), 2alpha-hydroxy ursolic acid (3), tormentic acid (4), daucosterol (5), maltol (6), luteolin (7), quercetin (8), apigenin (9), methyl brevifolincarboxylate (10), gallic acid (11), 3, 4, 8, 9, 10-pentahydroxydibenzo[b, d]pyran-6-one (12), and ellagic acid (13). Conclusion Compounds 3, 4, 6-13 were isolated from the plant for the first time. And compounds 3, 4, 6, 10, 12 were obtained from the genus for the first time.