Drying method is one of the main factors affecting the composition and quality of essential oil. In order to study the effect of drying method on the yields, compounds and biological activities of the essential oil extracted from Mentha longifolia L., shade-drying, sun-drying and oven-drying at 40℃ were used to dry the aerial part of Mentha longifolia L. in growing period which collected from Aksu of Xinjiang. In comparison with essential oil extracted from fresh Mentha longifolia L., steam-distillation was used to extract essential oils of Mentha longifolia L., and the effects of drying methods on the yields of essential oils were analyzed. Gas chromatography-quadrupole-time-of-flight-mass spectrometry was used to analyze the chemical composition of essential oil. The Gas chromatography-flame ionization detector was used to analyze the relative contents of compounds in essential oils, and the effects of drying methods on the composition and content of essential oil of Mentha longifolia L. was studied. DPPH and ABTS radical scavenging tests were used to study the effect of drying methods on the antioxidant activities of essential oil, and disk diffusion method was used to study the effect of drying methods on the antibacterial activities of essential oil. The results showed that drying methods had significant effect on the yields, composition and bioactivities of essential oil. The highest yield of essential oil was found in the shade-drying Mentha longifolia L. (0.49%±0.01%), followed by oven-drying at 40℃ (0.42%±0.03%), sun-drying (0.19%±0.02%) and fresh Mentha longifolia L. (0.12%±0.03%). Carvone (46.58%-50.75%) and limonene (24.01%-29.71%) were the main compounds of essential oil. However, the contents had significant differences. The results of antioxidant and antibacterial tests showed that there was no significant difference of antioxidant activity among the essential oil of Mentha longifolia L. extracted from three drying methods. However, antioxidant and antibacterial activities were much higher than the essential oil obtained from fresh Mentha longifolia L.. According to the yield and biological activities of essential oil, shade-drying could be considered as the best drying method of Mentha longifolia L..