In order to solve the problem of increased injection pressure and declined injection volume during late injection period of main slug of some alkali-surfactant-polymer（ASP）flooding injection wells in Daqing oilfield，a compound plug removal agent composed of inorganic ammonium degradation agent and compound acid was prepared. The plug removal effect on the plug from ASP injection well was studied in lab and blocking test was applied on the injection wells of Daqing oilfield. The results showed that this compound plug remover agent had good dissolve effect on the plug of injection wells with more than 98% dissolving rate. When the plug removal agent was applied on site，the degradation agent was injected first which used to degrade the clumps blocking of polymer，then the compound acid was injected which used to treat the residual scale and mechanical impurity. After the plug of 14 wells with ASP injection was removed，the average pressure of the wells in early days decreased 2.2 MPa，the average daily injection increased 12.5 m³，and the average period of validity reached to 183 days. The compound plug removal agent had a better decompression and augmented injection effect to ASP flooding injection wells which injectability declined because of plug in late injection period of main slug and side slug.