The volatile oils from leaf of Hibiscus syriacus L. ,which extracted by supercritical fluid extraction of carbon dioxide (SFE—CO2) and steam distillation extraction(SDE) were separated and identified by GC—MS, respectively. And then studied the lung cancer cell A549 inhibitory activities by inhibiting rate and cell apoptosis rate for lung cancer cell A549. Forty components were identified from the SFE—CO₂ volatile oil. Forty-seven components were identified from the SDE volatile oil. The SFE—CO₂ and SDE essential oils of the leaf showed their activities against lung cancer cells A549 with the inhibition rate of 80.08% and 62.75%, which indicated different volatile oils extracted by different methods had significant effect on their antitumor activities. The verification experiments showed that estra-1,3,5(10)-trien-17-ol, 1-hexyl-6-hydroxy-4-methylhexahydropyrimidin-2-thione, 6,6-dimethyl-9-(3-methyloxiran-2-yl)-1,4-dioxaspiro［4.5］decane, 2,4-bis(1,1-dimethylethyl)-phenol and eugenol were the main active components of inhibiting lung cancer cells A549.