Abstract: As the exploration and development of deepwater and ultra-deepwater oil and gas resources in the ocean proceed, the complex stratigraphic environment has brought more severe challenges to cementing operations. In an environment of ultra-deep water with low temperature, high pressure, and possibly natural gas hydrates, conventional cement slurry is difficult to meet the safety requirements of cementing operations. In order to achieve long-term and effective cementing, a set of cementing technologies applicable to ultra-deepwater development wells was developed, including a cement slurry with low heat of hydration suitable for ultra-deepwater and low-temperature environments. Compared with conventional cement slurry, the heat release of hydration of this cement slurry is reduced by more than 23%, effectively reducing the risk of hydrate decomposition and causing no effect on the strength of cement. In addition, a heat transfer model for marine ultra-deepwater wellbores was established. Based on the iterative solution of this model, a simulation and prediction software for marine ultra-deepwater bottom hole circulating temperature (BHCT) was developed, and the accuracy of the heat transfer model for marine ultra-deepwater wellbores was verified through the developed BHCT downhole measurement tools. Meanwhile, a highly efficient oil-based flushing fluid with good emulsification and wetting reversal effects was developed, which improved the flushing efficiency of oil-based filter cakes. The 11 development wells in Block X of the South China Sea have adopted the cementing technologies for ultra-deepwater development wells. The cementing construction went smoothly, and the cementing quality was excellent. Research and field applications show that the cementing technologies for ultra-deepwater development wells can solve the technical difficulties of cementing in the low-temperature, high-pressure, and possibly hydrate-containing environment of ultra-deep water, providing technical support for the development of ultra-deepwater oil and gas resources.