Abstract: The volatile oil components in Nostoc Commune were extracted by steam distillation (SD) and supercritical fluid extraction (SFE) and analyzed by gas chromatography-mass spectrometry (GC-MS).A lot of 80 volatile compounds were identified in Nostoc Commune,including 28 alkanes,9 vinyl compounds,9 esters,4 acids,5 ketones,4 terpenes,5 alcohols,7 aldehydes,1 heterocycle,1 phenol,1 epoxy,2 amines,2 etherses,1 anhydride class and 1 acetylene,with 8 compounds being detected in both.The great differences existed between the volatile constituents extracted by steam distillation and superitical fluid extraction methods.The volatile oils exhibited significant antioxidant activities in vitro in a concentration-dependent fashion.The volatile oils of SFE showed a stronger competence on ABTS·,DPPH·,the hydroxyl free radicals than the volatile oils of SD,and the maximum inhibition could be over 50%,its ED50 values of scavenging ABTS·,DPPH·and ·OH:9.954%,9.424%,11.394%(V/V) of the volatile oils of SD,8.267%,6.012%,9.121%(V/V) of the volatile oils of SFE.