Abstract: With the purpose of extending storage period of sweet sorghum stalks, the variations of respiration rate, sucrose invertase, polyphenoloxidase of postharvest sweet sorghum stalk were researched, and Modified Atmosphere Packaging(MAP) storage experiments with Low Density Polyethylene Membranes(LDPE) of different thickness were carried out. The results show that respiration rate of post harvested sweet sorghum stalk increases with the increase of temperature, and the respiration rate increases about twice when temperature increases from 10℃ to 30℃. The respiration rate of stalks of Liaotian No.1 sweet sorghum variety was higher than that of stalks of Liaoshiza No.1 sweet sorghum variety at the same temperature. Stalks of Liaotian No.1 and stalks of Liaoshiza No.1 performed anaerobic respiration at ten-day storage period under the conditions of 2.2% O₂, 7.6% CO₂, and at seventeen-day storage period under the conditions of 3.6%O₂, 6.4%CO₂, respectively. Besides, the activity of neutral invertase, acid invertase and polyphenoloxidase inside stalks of sweet sorghum in MAP storage presented an increasing tendency. The loss of total sugar content, increase of reducing sugar content and weight loss of stalks were 2.8%～20.9%, 134.3%～523.1%, and 1.37%～1.51%, respectively after thirty-day storage. The stalks of sweet sorghum inside Density Polyethylene Membranes(LDPE) with the package of 0.034 mm in thickness had a relatively low activity increasing extent of sucrose invertase and polyphenoloxidase, and a decrease of loss of the total sugar content. This research provides a scientific reference for solving storage problems of stalks during fuel ethanol production with sweet sorghum stalks.