The effect of polymer film on the biooxidation of arsenopyrite tailings was examined. Adsorption of a typical sugar polymer, dextrin, on the mineral particles was studied. The effect of pH on the adsorption at the biooxidation range was determined. The microelectrodes were used to measure the dissolved oxygen concentration in the polymer film. Based on these results, the oxygen diffusion coefficient has been calculated to be 1.6 10-5 cm2/s. The biooxidation results show that polymer film plays a key role in both the immobilization of microbial cells and oxygen diffusion. For effective biooxidation of arsenopyrite tailings the presence of polymer film onto the solid surface is indispensable.