Abstract: OBJECTIVE To analysis the volatile components from extract of trunk of Michelia macclurei Dandy. (ETMMD), and explore the inhibition of ETMMD on growth of MDA-MB-231 cell lines in vitro. METHODS The volatile components from ETMMD were extracted with steam distillation method and analysized by GC-MS. The relative content of each component was calculated by peak area normalization. The inhibiting action of ETMMD on growth of MDA-MB-231 cell lines in vitro were examined by MTT assay, and the apoptosis-inducing of ETMMD on MDA-MB-231 cell lines was explored by flow cytometry assay. RESULTS There were 42 peaks were detected, in which 41 compounds were identified, which made up 99.73% of the total volatile components. From MTT assay, the inhibition rates of ETMMD on growth of MDA-MB-231 cell lines in vitro were observed in concerntration-dependent manner, and the apoptosis-inducing of ETMMD on MDA-MB-231 cell lines was observed by flow cytometry. CONCLUSION The main components in the volatile components are sesquiterpene and unsaturated ketones, unsaturated esters, unsaturated fatty acid ester and steroids, etc. ETMMD can significantly inhibit the growth of MDA-MB-231 cell lines in vitro and significantly induce MDA-MB-231 cell lines apoptosis.