In order to develop safe， convenient and low-cost storage technology to improve the storability of postharvest navel orange fruit， and elucidate its possible mechanism， the harvested ‘Newhall’ navel oranges were treated with the chitosan， that is Kadozan with dilution of 1 ∶ 800 (VKadozan ∶ VKadozan + water)， for 5 min， and the ‘Newhall’ navel oranges soaked in water for 5 min as the control， then the fruit were stored at 80% relative humidity and (18 ± 1)℃. This work was studied the effects of chitosan treatment on the reactive oxygen species (ROS) metabolism and membrane permeability in harvested ‘Newhall’ navel orange fruit. The results exhibited that， compared to control ‘Newhall’ navel oranges， chitosan treatment could better maintain fruit appearance quality and effectively reduce fruit decay of 'Newhall' navel oranges during postharvest storage. Additionally， chitosan treatment could effectively suppress the increased cell membrane permeability， the increased contents of superoxide free radical， hydrogen peroxide and malondialdehyde， retain higher activities of superoxide dismutase， ascorbate peroxidase and catalase， higher contents of glutathione and ascorbic acid， and higher levels of reducing power and 1，1-diphenyl-2-trinitrophenylhydrazine free radical scavenging ability in 'Newhall' navel oranges during storage. Therefore， the treatment of chitosan， Kadozan with dilution of 1 ∶ 800 (VKadozan∶ VKadozan + water)， could effectively enhance the storability of harvested ‘Newhall’ navel orange fruit， which was associated with chitosan treatment enhancing ROS-scavenging ability to reduce the production and accumulation of ROS and malondialdehyde， and then alleviate membrane lipids peroxidation and maintain the better cell membrane structure integrity in postharvest ‘Newhall’ navel orange fruit.