Abstract: Abstract: Vacuum cooling is a rapid cooling technique extensively used for cooling some agricultural and food products. The vacuum cooling technology is now gradually applied to the precooling treatment of agricultural products due to the advantages of quick cooling, easy operation, no constraint of packing containers, and energy savings. Consumption of Agaricus bisporus has increased substantially because of its delicacy, flavor and nutritional value. Agaricus bisporus is an excellent source of several essential amino acids, vitamins (B2, niacin, and folates), and minerals (potassium, phosphorus, zinc, and copper). Agaricus bisporus has a short shelf life of 3-4 days compared to most vegetables at ambient temperatures because it has no cuticle to protect it from physical or microbial attack or water loss. Loss of quality is caused by morphological changes due to maturation, discoloration, changes in texture and flavor, and losses of nutrients. Textural changes of fruits are accompanied by loss of neutral sugars, solubilization and depolymerization of the polysaccharides of the cell wall, and rearrangements of their associations, as the result of the combined action of several cell wall-modifying enzymes, acting in both pectic and hemicellulosic fractions. Recent studies on the structure of the plant cell wall have disclosed a large number and type of biochemical linkages between the components. Such linkages are potential targets for enzymatic action and draw attention to the putative involvement of several members of enzymes able to act and modify its structure in a developmental and coordinated way. The objective of this study was to determine the effect of vacuum cooling treatment on cell wall compositional changes and ultrastructure in fresh mushrooms during 15 d of post-harvest storage at 4℃. In this study, we investigated the change of cellulose content, cellulose activity, propectin content, WSP content, and the PG activity of Agaricus bisporus before and after vacuum cooling. We also studied changes in those properties during storage. The results showed that vacuum cooling treatment could retard the increase of cellulose activity and PG activity and slow down the reduction of cellulose content and propectin content. At the end of storage, the contents of cellulose and propectin of Agaricus bisporus without vacuum cooling treatment were decreased by an average of 58.0% and 62.07%, respectively. The significant difference was found between the Agaricus bisporus without and with vacuum cooling treatment (P<0.05). No sign of damage could be observed as a result of vacuum cooling the Agaricus bisporus. During the storage, the Agaricus bisporus with vacuum cooling treatment retained its structure better than without vacuum cooling.