Essential oil was extracted from Hainan Pallavicinia subciliata(Austin)Steph.by accelerated solvent extraction(ASE),and its composition was analyzed by gas chromatography-mass spectrometry(GCMS),and computer retrievals were also carried out by using mass-spectrograms.Total 17 compounds were identified from the essential oil,in which phenanthrene,dibutyl phthalate,n-hexadecanoic acid,and propyl nitrite had relatively high contents,being was 41.54%,41.27%,11.57%,1.57%,respectively.