[Objective] Adsorption-desorption of Sb on micro-interfaces of soil colloids deeply affects its mobility, transformation and fate in the soil environment. Various soil minerals, organic matter (OM), microbes and soil colloids often combine with each other to form complicated mineral-organic complexes, which vary in properties (e.g., surface charge, particle size and the functional groups) with their composition and hence affect adsorption-desorption of the trace element differently. So far, though much have been done on the behaviors of antimony binding to single soil components, little attention has been paid to adsorption processes of Sb to mineral-organic composites and its mechanism.[Method] In this study, a batch adsorption experiment was carried out to investigate Sb (V/Ⅲ) adsorption behaviors on the interfaces of typical aluminum oxide-bacteria composites different in component ratio (30:70 and 70:30), with the aid of spectroscopic techniques and to validate whether bacteria affect Sb oxidation on mineral surfaces and to explore underlying mechanisms.[Result] Nano-sized particles of α-Al₂O₃ over on the surface of Bacillus cereus form an incomplete "mineral film", which may suggest that some of the available adsorption sites on either the mineral or the bacterial cells are covered or blocked. The Langmuir model can adequately describe Sb adsorption isotherms with a goodness of R²>0.98; α-Al₂O₃ adsorbs much more Sb (~50 mg·g^-1) than bacterial cells(15-24 mg·g^-1), which may be explained by difference in surface charge property, i.e., bacteria are negatively charged whereas α-Al₂O₃ is positively charged; the binding of Sb to α-Al₂O₃-bacteria composites does not follow the "component additive rule", i.e., the sum of the individual adsorptivities, but is significantly enhanced compared to the predicted assuming additivity. Scanning electron microscopy-energy spectrum analysis shows that the elemental distribution of Sb is highly correlated to that of Al rather than C, suggesting that Sb is mostly bound to minerals in the binary composites; and XPS analysis shows that the AlOH group of α-Al₂O₃ and the COOH and NH₂ groups of bacteria are all involved in binding Sb in the binary composite, possibly through formation of strong inner-sphere type complexes; moreover, bacteria inhibit oxidation of Sb (Ⅲ) on the surface of α-Al₂O₃, probably indirectly by hindering electron transfer between Sb and α-Al₂O₃.[Conclusion] All the findings in the study suggest that bacteria affect not only the quantity of Sb adsorbed onto Al minerals, but also oxidation-reduction of the element, therefore mineral-organic interaction should be taken into account in predicting transformation, translocation and fate of antimony in soils.