Studying reservoir damage caused by the quality of polymer-contained sewage provided the evidence for the feasibility of reinjecting polymer-contained sewage. Taking the SZ36-1 oilfield of the Bohai Sea as an example，with the help of polarizing microscopy，environmental scanning electron microscope，nuclear magnetic resonance and other means of microscopic analysis， the four significant indexes of water quality including the concentration of emulsified oil，suspended solids and produced polymer， and particle median size，were quantitatively evaluated by the core dynamic damage experiment，and the damage mechanism of reinjecting polymer-contained sewage to reservoir was also discussed. The results showed that the synergy effect between oil， suspended solids and polymer was the main damage source，and the damage degree of reservoir increased with increasing magnitude of single index of water quality. The deformable mass with high strength due to the adsorption and aggregation of polymer molecules，was the key factor to cause the blockage of pore throat. When the polymer-contained sewage invaded into the reservoir，the polymer preferred to block the large and medium-sized throat，and the blocked behavior gradually transformed from the interior to the exterior of filter cake. Optimizing the treatment process of sewage water and the current dosing method was the key to solve the treatment problem of polymer-contained sewage.