Chengdao Oilfield is a large shallower sea oilfield with an annual output of 217×104 t during the Ninth Five-Year Plan period. Since the reservoir showing the middle to high water-cut state，the development contradictions have become prominent. The offshore engineering supporting conditions cannot meet the continuous and stable production requirements of the oilfield，and the oil production has declined significantly with an annual decline rate of 2.5%. Therefore，the development adjustment is imperative. In view of the key problems restricting the continuous and stable production of Chengdao Oilfield，the key technologies of development and adjustment are developed in 6 aspects and 12 items through continuous research on the following aspects：reservoir geology，drilling and completion technology，injection-production and transportation technology，offshore engineering support，and platform life extension. The thin reservoir of fluvial facies in shallower sea is described and the geologic modeling at oilfield scale is established in details. The dense cluster drilling and completion technology for high angle cluster well and protection technology for multizone reservoir with complex pressure-drop profile，zonal water injection technology for high-angle well with long-interval，measurement and adjustment integration technology，high-efficiency zonal sand control and long-life high-efficiency lifting production technologies for high-angle well with long-interval are developed. The integration platform for oil and gas production and well repair and high-efficiency oil-gas-water treatment technology are developed as well. Platform testing and reinforcement technology for life extension in complex shallower sea environment are constructed. The successful application of the above technologies has ensured the high-speed and efficient implementation of scale subdivision of strata and well patterns adjustment in Chengdao Oilfield. The oil production reached 336×104 t in 2019.