Mentha longifolia. is a perennial herb of Mentha in Labiatae. Considering the biological activities of Mentha longifolia essential oils, this work was planned to study the yields, relative percentage content and semi-quantitative change of chemical constituents as well as the biological activities of essential oils extracted by different extraction methods. Steam-distillation (SD), lipophilic solvents (n-hexane) extraction (LSE) and supercritical CO2 fluid extraction (SC-CO2) were employed to produce essential oils from Mentha longifolia. The essential oil obtained from LSE (1.21 +/- 0.06%, w/w) showed the highest yield. A total of 39 compounds were identified by gas chromatography/flame ionization detector (GC-FID) and gas chromatography/mass spectrometry (GC-MS). The major compounds in SD and LSE were carvone, limonene, trans-caryophyllene and alpha-Terpineol, the major compounds in SC-CO2 were carvone, trans-caryophyllene, trans-beta-Farnesene and Germacrene D. All essential oils showed varying degrees of antioxidant and anti-COX-2 activity. The IC50 ranging from (0.69 +/- 0.01 similar to 15.61 +/- 0.16 mg/mL) for DPPH and (0.16 +/- 0.001 similar to 2.19 +/- 0.11 mg/mL) for ABTS, SC-CO2 produced essential oil showed the highest scavenging activity both on DPPH and ABTS. Meanwhile, all the EOs showed the strong inhibition activity on COX-2, the EO obtained by SC-CO2 also showed the highest capacity to inhibit COX-2.