Objective: To obtain the optimum condition for the extract of essential oil from Artemisia annua by different extract methods and analyze the chemical composition of the essential oil by GC-MS and evaluate the antimicrobial properties of the essential oil. Method: The fresh aerial part of A. annua was extracted by Soxhlet extraction and direct distillation to yield two essential oil samples designated as oil-1 and oil-2

respectively

which were both subjected to antimicrobial activity screening and GC-MS analysis. Result: The optimum condition for Soxhlet extraction was at a solid-liquid ratio1:7.8 and extraction time of 3 h

while for direct distillation at a solid-liquid ratio1:7.4 and extraction time of 5 h. Oil-1 displayed inhibitory activity against Aspergillus niger

Mycocentrospora sp.

Penicillium sp.

and Penicillium marneffei with MIC values of 1.25

1.25

5.0

and 1.25 mg·L-1

respectively

while oil-2 showed antibacterial activity toward Corynebacterium pekinense

Bacillus subtilis

tetracoccus

and Proteus vulgaris with MIC values of 0.023 5

0.023 5

0.005 9

3.75 mg·L-1

respectively. According to the results from GC-MS analysis

48 components from 55 peaks in the gas chromatogram of oil-1 and 39 components from 48 peaks in the gas chromatogram of oil-2 were identified. Conclusion: Comparatively

fungi were more sensitive to oil-1 in the antimicrobial test

which may be attributed to the antifungal components comprising 8.25% of the oil-1

including ketones

ethers

and oganic acids. However

oil-2 showed stronger antibacterial activity than oil-1due to the higher content of alkenes in oil-2 (65.42%) than that of in oil-1(26.49%)

since alkenes were the major antibacterial components of the essential oil.