The invention discloses a discharge treatment system for the produced water of a polymer flooding oilfield, and belongs to biochemical discharge treatment of tertiary oil recovery polymer-containing sewage of the oilfield. Sulfate reducing bacteria having polyacrylamide degradation ability are cultured and screened; the produced water of the polymer flooding oilfield is treated though a combined process comprising a sulfate reducing bacteria pretreatment unit, a hydrolytic acidification unit and a contact oxidation unit; the sulfate reducing bacteria pretreatment unit is used for partially degrading and removing residual HPAM (Hydrolyzed Polyacryamide) out of the sewage at first, so that the load of the subsequent treatment units is reduced; a low-intensity ultrasonic generator is used for increasing the activity of a microbial enzyme by performing irradiation treatment on the activated sludge so that the capacity of decomposition of microorganisms on organic matters is improved; several techniques are combined to achieve the synergistic effect for improving the overall treatment capacity and the applicability of the process to the produced water of the polymer flooding oilfield. The discharge treatment system provided by the invention is simple in process and easy to implement, and is expected to realize standard discharge of the produced water of the polymer flooding oilfield in combination with auxiliary units such as a sedimentation tank.