Abstract: The high-speed shear rate near the perforation hole of the injection well causes the polymer solution mechanical degradation and the viscosity loss is serious, which affects the oil displacement efficiency.The mechanism of the viscosity of the polymer solution at the perforation hole is analyzed.Effects of different parameters on the polymer solution viscosity and the viscosity loss in perforation hole are studied.Studies have shown that the polymer solution apparent viscosity and its sensitivity to flow rate decreases with increasing flow rate; its sensitivity to perforation hole size is stronger than that of perforation density; the solution viscosity is higher at high perforation density and large perforation hole diameter.To maintain viscosity effectiveness, there is a limit flow rate under specific perforation parameters.The polymer solution viscosity loss is sensitive to different parameters, and the higher rheological index, perforation density, perforation hole diameter and small size casing can reduce the viscosity loss.Through the research results of this paper, the perforation completion parameters can be reasonably selected to improve the polymer flooding efficiency.