The work aims to investigate the inhibitory effect and mechanism of calcium chloride combined with cold shock treatment on the freezing damage of Citrus reticulata 'Aiyuan' during express delivery at –15 ℃ in winter. The effects of calcium chloride combined with cold shock treatment on the metabolism of cell membrane and cell wall were studied by setting up the control group without pretreatment, the cold shock group by 0 ℃ ice water, the cold shock group by 0 ℃ calcium chloride solution and the calcium chloride solution group at room temperature. The calcium chloride combined with cold shock treatment could reduce the generation of malondialdehyde (MDA) by increasing the activity of peroxidase (POD) and reducing the production rate of superoxide anion and maintain the balance of reactive oxygen species metabolism, inhibit the increase of relative conductivity and better maintain the integrity of cell membrane, thereby reducing the occurrence of freezing damage. It could also maintain a better peel surface within 15 days after thawing and rewarming. In addition, it could increase the accumulation of proline in the fruit tissue in the later stage of storage, effectively maintain the osmotic balance in the fruit, prevent dehydration, and reduce the cell damage caused by ice crystal formation. At the same time, it could delay the degradation rate of pectin and cellulose by inhibiting the activity of polygalacturonase (PG) and cellulase (Cx), maintain the integrity of the cell wall, and keep better flesh crispness and peel hardness. The calcium chloride combined with cold shock treatment can significantly reduce the freezing damage of Citrus reticulata 'Ai Yuan' fruits during express delivery at –15 ℃ in winter, providing a theoretical basis for the application of anti-freezing technology in express delivery of Citrus reticulata 'Ai Yuan'.