Based on sequence stratigraphy, the authors analyzed the characteristic of hydrocarbon reservoirs enrichment in the sequence stratigraphic framework in Qikou sag. The research shows that hydrocarbon reservoirs enriched near the second order sequence interface in Qikou sag. Hereby, the authors proposed the thought that second order sequence interface+corresponding system tract in the third sequence correlatable sag slope break types=favorable exploration zone. It is the three elements coupling controlled the favorable exploration zone.