Abstract: Abstract: Longan ((Dimocarpus longan Lour.) is high value fruit produced in southern China. Due to its higher nutritional value and health benefit, consumers love the fruit. But longan is highly susceptible to aril breakdown during storage, which is the single most important factor affecting the quality and shelf-life of postharvest longan fruits. Previous studies have shown that aril breakdown is caused by changes in the structure of fruit cell tissue due to cell wall metabolism. Heat treatment is an environment-friendly postharvest physical treatment, which can insect disinfestation, decay control, ripening delay, modification of fruit responses to other stresses and maintain quality of harvested fruits and vegetables. The effects of hot-water treatment (HWT) on aril breakdown, cell wall component contents and cell wall-degrading enzyme activities in pulp of harvested longan fruits were investigated. This study aimed to determine the relationship between inhibition of longan cell wall metabolism by heat treatment and aril breakdown for achieving the control of aril breakdown and prolonging the storage period of harvested longan fruits. The harvested longan (cv. Fuyan) fruits were pre-treated with hot-water at 50℃ for 10 minutes, air dry, and then packed into sealed polyethylene bags (0.015 mm thickness) and stored at (15±1)℃for 10 days. Aril breakdown condition was observed, cell wall component contents and cell wall-degrading enzyme activities in pulp of harvested longan fruits were determined regularly during the storage. The results showed that aril breakdown index constantly rose during storage, water-soluble pectin (WSP) content first increased and then decreased, contents of ionic-soluble pectin (ISP), covalent-soluble pectin (CSP),, hemicellulose and cellulose decreased continuously. Activities of pectin pectinmethylesterase (PME) and cellulase (CX) rose at first but then declined. polygalacturonase (PG) activity reduced, andβ-galactosidase (β-Gal) activity firstly fell and then went up in the pulp of the control treatment of harvested longan fruits. Compared with the fruits in the control treatment, HWT could significantly (P＜0.05) inhibited the rise of aril breakdown index, reduced the activities of the PME, PG, β-Gal and CX, delayed the increase in the content of WSP and the decline in contents of ISP, CSP, semicellulose and cellulose. From the results, it can be concluded that aril breakdown and components of cell wall metabolism in the pulp of harvested longan fruits were closely related. PME, PG and CX played an important role in the early aril breakdown, and β-Gal and reactive oxygen may play an important role in the late aril breakdown. Furthermore, the study also showed that HWT can reduce the degradation of the cell wall components by reducing cell wall-degrading enzyme activities in the pulp of harvested longan fruits, which helped to maintain the integrity of the cell wall structure, slowed down the leakage of cellular contents, and inhibited the occurrence of aril breakdown. The results provided reference of heat treatment for freshness-keeping of harvested longan fruits.