Objective To investigate the effect of interval ventilation time on the quality of fresh shiitake mushrooms under 55 kPa hypobaric pressure condition at 20 益 . Methods The shiitake mushrooms packaged in vacuum tank were treated with ventilating once every two days and daily ventilation, respectively. Respiratory intensity, weight loss rate, soluble solids content, polyphenol oxidase ( PPO) activities, malonydialdehyde ( MDA) content and sensory index were determined every two days. Results The results showed that daily ventilation treatment could inhibit the appearance of off- odor, significantly reduce the respiration intensity and maintain higher soluble solids content of shiitake mushrooms during vacuum tank packaging storage ( P<0. 05) . While the ventilating once every two days let shiitake mushrooms maintain higher overall sensory qualities, significantly inhibited the increase of PPO activities, and retarded the decrease of MDA content ( P<0. 05) . Conclusion The ventilating once every two days significantly reduced the weight loss of shiitake mushrooms in the late storage ( P<0. 05) .