The availability of Cr(VI) is usually used for assessing the phytotoxicity of Cr(VI)-contaminated soils. Although Cr(VI) can be reduced to Cr(III), the availability of Cr(III) in acid soils may be high and thus the phytotoxicity of Cr(III) cannot be ignored. Therefore, determination of the availability of both Cr(VI) and Cr(III) in acid soils is essential for assessing the phytotoxicity of Cr(VI)-contaminated soils. Two acid soils, Picchen and Neipu, were spiked with six levels of Cr(VI)(0, 150, 300, 500, 1000, and 1500 mg/kg). Two selective resins, DOWEX-M4195 and Chelex 100, were used to extract soil available Cr(VI) and Cr(III) respectively. Wheat seedling growth experiments were used for evaluating the phytotoxicity of Cr(VI)-spiked soils. The results showed that the growth of wheat seedlings was negatively correlated to soil DOWEX-M4195 extractable Cr(VI). Significant amounts of Cr(VI) were found being reduced to Cr(III) in two tested soils by X-ray absorption near-edge structure spectroscopy. However, the amounts of soil Chelex extractable Cr(III) were small. It suggested that the phytotoxicity of these two Cr(VI)-spiked acid soils was mainly resulted from having high amounts of soil available Cr(VI).