Abstract: The essential oil was extracted by hydrodistillation, and the best extraction technology were studied through single factor experiment and orthogonal experiment.The antioxidant and antimicrobial activities of the essential oil from Piper betle L.were investigated.The results indicated that the optimal conditions were solid-to-liquid ratio 50∶ 1000 g/m L, ultrasonic time of30 min, extraction temperature of 70 ℃, ultrasonic power of 192 W, heated refluxed of 4 h, the extraction rate of Piper betle L.essential oil was 2.96%.The IC₅₀ of the oil for scavenging activities against DPPH free radical and hydroxyl free radical were33.19 μg/m L and 71.11 μg/m L. The oil had certain antibacterial activity on the microorganisms, the minimal inhibitory concentration of Staphyloccocus aureus, Bacillus subtilis, Escherichia coli, Bacillus cereus, Micrococcus tetragenus, Sarcina lutea, Staphylococcus albus, Aspergillus niger, Mucor, Penicillium were 0.625, 1.25, 0.625, 0.625, 0.625, 2.50, 1.25, 0.313, 0.625, 0.313 mg/m L, respectively. In conclusion, the essential oil from Piper betle L. had strong antioxidative and antibacterial activities.