Pot experiment of rice seedling and culture experiment of ryegrass seedling in three kinds of typical soils with different total selenium (Se) content levels sampled from Ding’an County of Hainan Province were conducted to select optimal extractants from H2O (pH4.5), 0.5 mol/L NaHCO3(pH8.5) and 0.1 mol/L KH2PO4 for determination of available Se content. The results indicated that significantly positive correlation (p＜0.01) was found between available Se contents extracted by the 3 kinds of extractants and Se contents in plants. Available Se content extracted by H2O was very low. In pot experiment of rice seedling, compared with NaHCO3, the extraction time of KH2PO4 was shorter, the variation coefficient of available Se content was lower and the correlation coefficients was higher between available Se content and Se content in rice plants, therefore, 0.1 mol/L KH2PO4 was more suitable for determination of available Se of paddy soils in Hainan.