Abstract: As for the increasingly complicated exploration situation in the old oil areas in East China, this article proposes an ^“oil-assumed deduction^” assessment method, which is a backstepping evaluation of exploration targets based on the fundamental principle for oil and gas accumulation system. The process of the method is focused on the targets of traps in mature exploration of basins while centering the main factors controlling oil and gas accumulations, thus making comprehensive analysis and study of the petroleum geological conditions. The relative oil and gas accumulations model is established to fulfill the objective for gradual reduction of exploration risks and attainment of marginal effects. As compared to the traditional method, this method not only improves exploration of oil and gas abundant zones and evaluation efficiency for potential targets but also gets rid of restrictions from the past exploration experiences, offering an effective measure for exploration of increasingly complicated oil and gas abundant sags. The mindset of basckstepping evaluation is also suitable for settlement of exploration bottlenecks in the ^“oil and gas enriched sag^” field. With this method used to identify the main factors controlling oil and gas accumulations, breakthroughs have been made in basement exploration of Anfutun and Gaosheng buried hill areas, opening up the new field of lithological stratigraphic oil and gas exploration.