To study the chemical constituents from the roots of the Mongolian medicine Inulae Radix.The compounds were separated and purified by RP-HPLC and silver nitrate silica gel chromatography,and the structures of the compounds were identified by applying NMR and MS spectroscopy.Twenty-two monomeric compounds were isolated and identified as follows:5α,6α-dihydroxy-eudesma-11(13)-dien-12,8β-olide(1),4α-hydroxy-5-methoxy-5,8α-dimethyl-3-methylenedecahydronaphtho［2,3-b］furan-2-one (2),1(10),4(5),11(13)-germa-cradiene-8,12-olide (3),alantolactone (4),isoalantolactone (5),11,13-dihydro-5(6)-dine-alantolactone (6),alloalantolactone (7),4α,5β-epoxy-1(10),11(13)-germacra-dien-12,8α-olide (8),sseptuplinolide (9),8-epi-ivangustin (10),santamarine (11),racemosalactone A (12),3-oxo-eudesma-4(11)-dien-12,8β-olide (13),telekin (14),igalane (15),macrophyllilactone E (16),4α,15-epoxy-isoalantolactone (17),11,13-dihydroxy-alantolactone (18),1(2),4(15),11(3)-eudesma-trien-12,8β-olide (19),linolenic (20),linoleic acid (21),oleic acid (22).Compound 1 was a new sesquiterpenoes.Compounds 2,3,9-14,17,19-22 were isolated from genus Inula for the first time.Compounds 4-8,15,16,18 have been reported from Inulae Radix.