In order to produce selenium-enriched crops and provide a theoretical basis of phytoremediation to selenium contaminated soil, pot experiment and lab analysis were carried out to examine the differences of selenium uptake pattern and bioavailability to pakchoi (Brassica chinensis L.) when amended with selenate and selenite. Meanwhile, dynamic changes of soil available Se was analyzed to explore the reason. The results showed that no significant differences in pakchoi shoot biomass between selenate and selenite treatment were observed. The Se concentration in pakchoi decreased rapidly across time in the selenate treatments, while increased with the growing period in the selenite treatments. For the selenate treatments, the pakchoi shoot Se concentration was significantly higher than that in roots, but the opposite results were found in the selenite treatments. In the whole growth period of pakchoi, Se concentration in selenate treatment was 2-60 times higher of that in selenite treatments. The content of available Se in soil slightly decreased with the growth of pakchoi in the selenite treatments, but it decreased rapidly in the selenate treatments. The significant correlations between soil available Se and Se concentration in shoots and roots of pakchoi was found in selenate treatments, the correlation coefficients were 0.901 and 0.864, respectively. On the contrast, no significant correlation was observed between soil available Se and Se concentration of roots and shoots in selenite treatments. The results indicated that the differences between the Se uptake pattern of selenate and selenite on pakchoi were the comprehensive function of the ability of soil providing Se and crop uptake ability.