Sesquiterpenes were the main allelopathic active ingredients in Ligularia plants and often exhibit phytotoxic activity.In order to find the major compounds from allelochemicals for developing the eco-friendly natural herbicides,the phytotoxic eremophilane sesquiterpenes in Ligularia cymbulifera were studied.Thirteen eremophilane sesquiterpenes were isolated and purified by several chromatographic techniques from the root of L. cymbulifera.Their structures were identified by physicochemical property and analysis of spectroscopic data,including a new eremophilane sesquiterpenes,ligulacymlactam A（1）,3β-angeloyloxy-8β-hydroxyeremophil-7(11)-ene-12,8α(14β,6α)-diolide（2）,8β-hydroxyeremophil-7(11)-en-12,8α-olide（3）,10β-hydroxy-8β-methoxyeremophilenolide（4）,6β,8β-dihydroxyeremophil-7(11)-en-12,8α-olide（5）,8β-H-eremophil-3,7(11)-dien-12,8α;15,6α-diolide（6）,8β-hydroxyeremophil-3,7(11)-diene-8α,12(6α,15)-diolide（7）,8β-methoxyeremophil-3,7(11)-diene-8α,12(6α,15)-diolide（8）,eremophil-7(11)-ene-12,8α,14β,6α-diolide（9）,8β-hydroeremophil-7(11)-en-12β,8α(14β,6α)-diolide（10）,3-(methacryloyloxy)furanoeremophilan-15,6α-olide（11）,furanoeremophilan-14,6α-olide（12）,10β-hydroxy-6β-isobutyrylfuranoeremophilane（13）.The phytotoxic activities against A. thaliana of compounds 1-13 were measured by agar germination method.None of them showed inhibitory activities on seed germination,but some of them could promote the germinate time earlier than blank about 1-2 days.As well as,all compounds showed weak root growth inhibitory activity,and compound 13 was the most active compound (EC₅₀ =44.15±5.21 μg/mL).Further structure-activity relationship analysis suggests that the furanermophilane sesquiterpenes which containing the 10-position hydroxyl group and the 6-position side chain substitution have potential to be the lead compound for eco-friendly natural herbicides.