The invention relates to a treating agent which contains polymer produced liquid, which is applied in polymer oil displacement or weak gel which contains polymer, displaces oil and stores produced liquid. The invention is characterized in that percentage by weight of each component is that viscosity reductant, which comprises ferrous sulfate (FeSO4.7H2O), wherein the dosage is 2.5%-25%, or potassium permanganate (KMnO4), whose dosage is 0.5%-10%, additive which comprises ferric chloride(FeCl3), wherein the dosage is 0.05%-1.25%, stabilizing agent which comprises acetic acid whose dosage is 0.1%-0.75%, or citric acid whose dosage is 0.25%-1.25%, and rest is water. The treating agent has the advantages that the treating agent has viscosity reducing effect to produced liquid which contains polymer with different polymer contents. The treating agent adopts KYHPAM and 3730A polymer to respectively allocate simulated produced fluids, when the content of polymer is 50-1000mg/L, optimum dosageof next treating agent of each content is added, solution viscosity under indoor temperature can be lowered to 3.0MPa.s(which is equal to formation water viscosity 3.0MPa.s which is measured under the same condition), thereby eliminating the influence of polymer viscosifying effect to the settling separation of oil and water.