Abstract: In order to improve the hydrophobicity and the flotation effect of high-ash oxidized coal, adsorption and desorption of the Gemini surfactant onto high-ash oxidized coal were studied. FTIR and wettability heat measurement were used to study the differences between adsorption and desorption of the Gemini surfactant onto organic matters and minerals. The hydrophobicity and flotability of high-ash oxidized coal adsorbed Gemini surfactant effectively promoted with the surfactant concentration. Moreover, the ash of washed coal was increased due to adsorption of Gemini surfactant onto the minerals. The results of hydrothermal pretreatment show that desorption of the Gemini surfactant from organic matters and minerals is different. It was proved that the hydrothermal pretreatment before flotation operation lead to clean coal ash decreasing efficiently.