Salt contamination of soils due to climate change is a serious environmental issue facing the crop production today. High salt concentration inhibits seed germination, adversely affects the growth and productivity of crop plants. Rice is considered generally to be sensitive to salt stress during the growth period. However, the mechanism of rice plant cellular and molecular responses to salt stress is not fully understood. The present study investigated biochemical and molecular changes in rice root under salt stress. Compared with control treatment, 100 mM NaCI solution significantly inhibited root growth. The root growth rate and root fresh weight were decreased significantly, to appromaxitely half the rate with control treatment. In addition, salt stress strongly induced reactive oxygen species (ROS) production and Ca2+ accumulation in rice roots. Using Schiff reagent, ROS-induced lipid peroxidation in rice roots was indicated. Level of lipid peroxidation increased with increasing concentration of salt solution treatment. Semi-quantitative RT-PCR analysis revealed that some protein kinase-related genes (DUF26, WAK), signal transduction-related genes (CaM, MAPKKK, CDPK), transcription factor-related genes (OsWRKY, AP2/ERF) and ROS-related genes (OsGST, OsPrx, SOD) were up-regulated under salt stress. Polyacrylamide gel electrophoresis and activity-gel assay showed that enzymatic activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were strongly induced during salt treatment. Moreover, glutathione content, the most important intra-cellular defense against the deleterious effects of reactive oxygen species, increased significantly during salt stress in rice root. Taken together, these finding sheds light on the biochemical and molecular mechanism in response to salt stress in plants.