Abstract:This paper was conducted to study the change of mass loss and antimicrobial activities of hydrodistil－ lation extracts of cinnamon oil stored under different storage ways employing two methods，namely gravimetric and agar-hole diffusion assays and the amount of trans-cinnamaldehyde in cinnamon oil was also analyzed by gas chromatography-mass spectrometry （GC-MS）. Results showed that antimicrobial activities of cinnamon oil stored under different storage ways declined with the increase of time. Sealed stored in the dark at cold or room temperature （do not refrigerate）was a safe way for cinnamon oil to decrease its volatility and to maintain longer antibacterial activities. Antibacterial activities of cinnamon oil improved with the increasing of its concentration． Although，the inhibitory rate of cinnamon oil against tested strains reducing with time increasing， cinnamon oil sealed stored in the dark at room temperature at a concentration of 111.0 mg/mL still remained 50 % inhibition on the growth of the tested strains after 82 days，which suggested that cinnamon oil sealed stored in the dark at room temperature can be used as a natural preservative providing longer antibacterial activities and prolonging shelf life of fruits and vegetables．