In order to solve the technical problem of injected fluid channeling in offshore oilfields,the basic performance evaluation of plugging agent,core hole plugging rate and the large⁃scale dominant channel treatment experiment of "plugging + profile control" oil increase and precipitation effect was carried out in Bohai reservoir. The results show that the blocking rate of blocking agent for large⁃scale dominant channel is higher than 90%,which indicates that it can meet the technical requirements of blocking large⁃scale dominant channel in Bohai reservoir.Combining the large⁃scale dominant channel plugging technology with chemical profile control and flooding technology,the dual effects of macro and micro fluid flow diversion can be obtained,and the effect of oil increase and precipitation is very obvious.Compared with hydrophobically associating polymer solution,although the viscosity of Cr3+ polymer gel is relatively low,the polymer molecular aggregates in Cr3+ polymer gel have "intramolecular" cross⁃linking structure characteristics,and have better compatibility with reservoir pores,which can establish an effective displacement pressure gradient in deep core,resulting in better fluid diversion effect and larger recovery.