A method for improving injectivity of a polymer profile control and flooding system includes: respectively measuring surface Zeta potentials of suspended solids in sewage of an oil field site and a profile control and flooding agent; when the surface Zeta potentials of suspended solids in sewage of the oil field site are positive and in a range of -5mV-0, adding an anti-flocculation agent into the sewage of the oil field site before the profile control and flooding agent is added into the sewage of the oil field site, so that the surface Zeta potentials of suspended solids in a finally obtained mixture are negative and larger than 10mV in absolute value. The method for improving injectivity of the polymer profile control and flooding system has advantages that oil field sewage can be directly used for preparation of profile control and flooding liquid, additional filter devices are not needed, the problems of accumulation and blockage of a wellbore area can be effectively prevented, operation continuity is guaranteed, and operation cost is reduced.