Abstract: In order to understand the absorption and resistance mechanism of Se on tobacco, a hydroponic experiment was conducted to study the absorption and subcellular distribution of Se in tobacco leaves under different concentrations(0, 2, 5, 10, 20 mg/L)of Se(VI) and Se(IV). The results showed that(1)At low concentrations(<2 mg/L)Se improved the growth of tobacco plant, but it showed obvious inhibitory effects to tobacco plant at high concentrations(>5 mg/L)and the negative effects of Se(IV) were more serious than Se(VI) at the same concentration of Se.(2)The content of Se in different parts of tobacco plant increased significantly with the application of different valences of Se. The Se forms in leaves were mainly organic Se, and Se(IV)was the dominating form of inorganic Se.(3)For leaves and stalks the affinity of selenate was higher than selenite and for roots it was the opposite.(4)Se was mainly stored in the cytoplasm, and then the cell wall, with the mitochondria, chloroplasts had less Se.(5)The Se content of leaves, Se in the cell wall and cytoplasm from the Se(VI) treatment were higher than the Se(IV)treatment, suggesting that plants have better absorption ability and tolerance to Se(VI)than Se(IV). The reasons for this was that Se(VI)was easier to be used in synthesizing proteins or amino acids and be fixed in the cell wall such that the toxicity of Se was alleviated.