The influences of different fixed ways of polyurethane on the purification performance of wastewater treatment in biological contact oxidation were discussed, the polyurethane was put into biological contact oxidation by up-floating, sinking and general up-floating general sinking respectively, the relationship between microbial community structure and purification performance was analyzed. The results showed that polyurethane fixed by general up-floating general sinking could most efficiently remove pollutants, the purification rate of COD and NH+₄-N were 90％ and 94％; the attached microbial populations were with the largest number, the highest diversity, the strongest activity and the most reasonable function in this way. Therefore, the purification performance was affected by the fixed way of polyurethane in biological contact oxidation and the general up-floating general sinking was the most effective fixed way.