Abstract: OBJECTIVE To study the constituents of volatile oil in Apocynum venetum L. from various habitats and different species. METHODSThe volatile oil was extracted by water distillation method and analyzed by GC-MS. RESULTSThe constituents of volatile oil in Apocynum venetum L. from various habitats and different species have obvious differences. The main constituents from Yuncheng Apocynum venetum L. represented 31.78% of the total oil,oxacyclododeca-6, 9-dien-2-one, 7-methyl,fluorene,phytol, 3-tertbutyl-4-hydroxyanisole,piperonylamine,phenanthrene were found firstly.The main constituents of the volatile oils from Dongbei Apocynum venetum L.found firstly were benzene,1-(1,5-dimethyl-4-hexenyl)-4-methyl,tetradecanal.The main constituents of the volatile oil from Shanxi Apocynum venetum L. represented 39.89%,longifolene,cedrene,5,9-undecadien-2-one,6,10-dimethyl-(E),n-Hexadecanoic acid,hexadecanoic acid,methyl ester were found for the first time.Lastly the main constituents from Yuncheng Pocynum hendersonii W.represented 19.88% of the total oil,most of them were saturated hydrocarbons.CONCLUSIONEssential substances are different in quantity and quality in various habitats and different species. The main constituents of the volatile oil from Apocynum venetum L. should be made use of differently.