The cytoplasm membrane permeability (CMP), reactive oxygen species (ROS) and the activities of protective enzymes (APX, CAT, POD and SOD) of citrus (Citrus unshiu Marc.cv.) leaves under different red soil moisture treatments (levels) were studied. The results showed that malondialdehyde (MDA) and CMP of citrus leaves increased evidently and superoxidation of lipid metabolism also aggravated as soil relative water content (SWC) reduced. Both MDA content and CMP were significantly correlated with SWC (R2 = 0.9051* and 0.8236*, n = 50, respectively). Both superoxide anion radical (O2.-) producing rate and H2O2 content reduced with the decrease of soil water content. However, this was not the single reason that O2.- and H2O2 led to the oxidative damage of citrus leaves under red soil drought conditions. The anti-oxidation system of citrus leaves was in the homeostasis as SWC changed. The activities of SOD, POD and APX remained high under the deficit of soil water, while CAT activity decreased rapidly with the decrease of SWC.