Bentonite produced in Xiazijie, Xinjiang (China) was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG) and cation exchange capacity (CEC). The bentonite is composed of dioctahedral montmorillonite with predominant quantity, certain amounts of quartz, feldspar to be characterized as typical sodium bentonite. In order to bleach cottonseed oil, optimum conditions for sulfuric acid activation of the raw bentonites were investigated, which were obtained by selecting various acid strength, at 96-98℃ and activating for 4h with 1: 2 solid-liquid ratio. The acid activation bentonites were suitable for decolorization of cottonseed oil through removing carotene and chlorophyll. The bleaching capabilities of different pigments with activated bentonite with treatment of 25% sulfuric acid were 70.3%, 73.1%, 83.2%, 81.8% and 88.9%,respectively. Bleaching with acid activated bentonite gave oils lower peroxide values and acid values.