The genus Ligularia, of the Compositae family, consists of about 150 species in the world, with more than 100 distributed mainly in northwest and southwest China. About thirty Ligularia species have long been used as folk medicines in China. Their roots, stems, leaves and flowers possess the efficacy of relieving internal heat or fever, reducing phlegm and relieving a cough, invigorating the circulation of blood and stopping pain, as well as antibiotic and anti-inflammation effect. Their main bioactive components are eremophilane sesquiterpenes and pyrrolizidine alkaloids (PAS).In order to explore many more medical potential plants of Ligularia species and to exploit new resources of Chinese traditional medicine, this thesis studied the chemical constituents of the roots of L. muliensis Hand. Mazz., collected from Muli Autonomous County, Sichuan Province. Its essential oil was analyzed firstly by capillary GC-MS method. The chemical constituents in the rest part were isolated by means of silica gel column chromatography (CC), preparative thin layer chromatography (PTLC) and recrystallization etc., and 44 compounds were obtained. The structures of 35 compounds were elucidated by spectroscopic methods: IR, UV, EI-MS, FAB-MS, HR-MS, ID NMR (~1H NMR, ~(13)C NMR, DEPT and NOED), 2D NMR (~1H-~1H COSY, HMBC and NOESY) and CD, along with a comparison with authentic samples or the data from literature, as well as some chemical transformations. They were identified as monoterpenes, sesquiterpenes, triterpenes, sterols, lignin, flavonoids etc., 9 of which are new compounds. Furthermore the bioactivities of some compounds were studied by using SRB (sulforhodamine B) method to evaluate their cytotoxic activity against human leukaemia cell (HL-60), human hepatoma cell (SMMC-7721) and human cervical carcinoma cell (HeLa). In addition the anti-FflV-1 PR activity of one lignin compound was tested and the compound exhibited slight positive effect.In the end one review has been made of the bioactivities and synthesize of the eremophilane sesquiterpenes reported in the past twenty years.The results of this investigation were expected to enrich the database of natural products, to afford important academic basis for the exploitation and utilization of natural resources and to supply a significant scientific basis for pharmacology, chemotaxonomy and screening of new medicines.