The treatment of oil-bearing sew age of polymer f looding is more dif ficult than the treatment of oilbearingsew age of conventional water flooding, because the viscosity of oil-bearing sew age of polymer f looding ishigh and the oil droplets are smaller.The st ructures of hy drocyclone are ameliorated and the operating parametersare optimized throug h experiment s in situ.The optimized hy drocy clone is suitable for t reating the sewage ofpolymer flooding.And, the experimental result s show that when the initial oil content is under 2 000 mg/ L, theoil content of oil-bearing sew age t reated by the hydrocyclone is under 153 mg/L, and the f inal water quali ty af terfiltratio n reaches the standard of middle saturated st ratum of injected water.