Abstract: In the deepwater areas in the South China Sea, the marine environment is inclement, typhoon and isolated internal wave frequently occur, and the engineering design and operation of deepwater drilling and completion feature great difficulty and high risk. In order to improve the exploration and development technology of deepwater oil and gas in China, and realize the leapfrog development of technical research and development, engineering design and operation capacity of offshore drilling and completion from shallow water to deepwater and ultra-deepwater, after about 10 years technological breakthroughs and operation practices, the key technical system of deepwater drilling and completion with proprietary intellectual property rights has been formed, the operation guide, technical standard and specification system of deepwater drilling and completion has been established for the first time, the technical challenges and operation difficulties under special environmental conditions in the South China Sea have been overcome, the safe and efficient operation requirements of deepwater oil and gas drilling and completion have been satisfied, the first batch of deepwater wells with the maximum operation water depth of 2 500 m have been drilled, and the new journey in the deepwater oil and gas exploration and development of China has been started.