Abstract: Deep wells in deep water are facing with special geological conditions such as super depth, ultra-high temperature, ultra-high pressure, and complex reservoirs, which put forward higher requirements for the comprehensive mechanical properties of cementing cement. Thus, there is an urgent need for solidification conservation and preparation methods of set cement under high-temperature and high-pressure working conditions, so as to evaluate and optimize the cement slurry system accurately and reliably. A solidification conservation device for high-temperature and high-pressure cement slurry and a method for preparing set cement were established to simulate the cement slurry solidification conservation process under high temperature and high pressure (150 MPa, 250 ℃) in deep wells in deep water. Besides. The mechanical properties such as uniaxial compressive strength and tensile strength of set cement prepared under different temperature and pressure conditions were analyzed and compared. The results show that the established cement solidification conservation and preparation method under high-temperature and high-pressure conditions can accurately simulate the high-temperature and high-pressure wellbore conditions of deep wells in deep water, and at the same time, the high-temperature and high-pressure conditions can also give full play to the performance advantages of the additives in cement slurry system. The set cement prepared by this method shows significant advantages in mechanical properties such as compressive strength and tensile strength compared with the set cement prepared by conventional methods. The proposal of this method is conducive to promoting the development of solidification conservation of high-temperature and high-pressure cement slurry system in deep wells in deep water, as well as the development of set cement preparation technology, which provides an experimental method and technical support for the optimization of cement slurry system formulations.