In order to explore the annual change of essential oils contents and their chemical compositions from the leaves of E.exserta and E.urophylla, the essential oils were extracted in different months with steam distillation respectively and their chemical compositions were determined with GC-MS. The best harvest time of the essential oils were confirmed according the extraction ratio of the essential oils. The results showed that the extraction yied of essential oils from the leaves of E.exserta showed a significant seasonal change while the essential oils from E.urophylla did not. The extraction yield of essential oils from E.exserta in May, September and October were relatively higher and the leaves of these months were suited for extracting essential oils. The major compositions of the essential oils from E.exserta were α-pinene, β-pinene, eucalyptol and the major constituents of essential oil from E.urophylla were α-pinene, eucalyptol, borneol, α-Terpineol. The content of major compositions in each month varied considerably.