Abstract: In order to understand the changes of the content and composition of essential oil from M.bracteata at different parts and different months,the essential oil in leaves of M.bracteata was extracted by steam distillation from January to late December 2017,and then essential oil composition was analyzed by gas chromatography-mass spectrometry.The results showed that the contents of essential oil were 0.282% and 0.268% in old leaves and new leaves of M.bracteata,while the contents of essential oil in roots,stems and branches were very low.In one year,the content of essential oil in August was the highest,with 1.10%;in January,it fell to the trough,with 0.25%;Methyl eugenol was the main components of essential oil.The content of essential oil in M.bracteata shows a higher level in the condition of high temperature and humidity.The research results discovered that the change law of contents and compositions of essential oil in different months and different parts of M.bracteata,this provides scientific basis for the efficient utilization and development of M.bracteata essential oils.

Key words: M.bracteata, essential oil, steam distillation method, GC-MS