Abstract: Xihu Sag is a major oil and gas production area in East China Sea. At present, most oil and gas fields have entered the middle or final development stage, with rapid production decline, poor production measures and insufficient reserve replacement resources. The stable production situation of oil and gas fields is grim, and development adjustment is imperative. In recent years, the efficient development and adjustment strategy of focusing on contradiction analysis to identify the problem, focusing on fundamental research to determine favorable fields, focusing on technological innovation to enhance development capabilities, and focusing on the whole-process optimization to increase efficiency was used to achieve a double breakthrough in understanding and technology. The deployment and implementation of 52 adjustment wells in the development fields have achieved excellent effect. It effectively reversed the production decline trend of the Xihu oil and gas field, and continuously created new records in oil and gas production, forming a number of key technologies to support the effective development of Xihu Sag, which laid a solid foundation for the continuous increase of reserves and production in East China Sea.