Abstract: Changes of physiological and biochemical characteristics of Citrus grandis Osbeck cv. Guanximiyou plants under salt stress were studied in hydroponics culture experiments.The results show that with the increase of salinity and treated time,the root vitality,relative water content (RWC),pH value of cell sap in leaves and the contents of photosynthetic pigments and amino acid decrease,but the macromolecule leakage value and the content of malondialdedyed (MDA)in leaves increase.There is a significant correlation between physiological and biochemical characteristics.The root vitality and the content of MDA in leaves are sensitive to salt stress and the decrease of root vitality may be the earliest response of Guanximiyou pomelo plants to the salt stress.