Abstract: As the development of polymer flooding, polymer contained blockage was appeared and the oil well production was decreased in SZ36-1 oilfield. In this paper, the components of blockage in polymer flooding injection well (PFIW) and response well (PFRW) were compared by several characterization methods firstly. The inorganic scale was the main substance in collected samples, the mass ratio of inorganic scale and organic scale in PFRW blockage was 4.0-5.5, which was much larger than that of PFIW (0.25-0.75). The inorganic scale mainly was Fe₂O₃ in PFIW and and CaCO₃ in PFIW, and the organic scale was partially hydrolyzed polyacrylamide. Then, the formation mechanisms of inorganic scale and organic scale in PFRW and PRIW were investigated, especially the formation mechanism of blockage in PFRW was studied. In the area which was close to the response oil well, there was a lot of Fe³⁺ in residual acid solution after the acidification operation, and when it was mixed with polymer flooding solution, Fe(OH)₃ was formed as the pH increased and Fe₂O₃ blockage was formed after the oxidation. In addition, the cross-linked polymer blockage which was organic scale, was formed by the selective coordination between polymer and Fe³⁺ when the degraded polymer was mixed with Fe³⁺ solution in acid condition. The results in this paper are helpful for the targeted removal of plugging in PFRW or PRIW and preventive blockage in PRIW.