In recent years, with the exploration and development in China advancing into deep and ultra-deep reservoirs, cementing operations in ultra-deep and complex geological conditions face numerous technical challenges. The pressure system in the formations becomes complex from top to bottom, reservoir fractures are developed, and hydrocarbon displays are active. Additionally, there are ultra-high temperature and ultra-high pressure wellbore conditions. During the drilling and completion stage of ultra-deep complex gas wells, the contradiction between pressure stability and leak prevention becomes prominent. Challenges include difficulties in optimizing the displacement environment during cementing, ensuring displacement efficiency, and balancing cement slurry filling and interfacial bonding degree. Various factors collectively restrict the further enhancement of wellbore integrity. To address these challenges, a dynamic fine pressure control cementing technology for ultra-deep high-pressure gas wells within a narrow safety density window has been developed based on numerical simulation studies of ultra-deep wellbore circulating pressure loss calculation models and the integration of a fine pressure control drilling system. This technology enables dynamic adjustment of wellhead back pressure throughout the entire process of circulation, cementing, displacement, and pump start-stop, allowing for precise control of wellbore pressure distribution and ensuring that the Equivalent Circulating Density (ECD) during the entire cementing process stays within a safe density window. Field applications have demonstrated that this technology effectively resolves the pressure stability and leak prevention contradiction within a narrow density window, successfully achieving safe and efficient one-time returns of cement slurry in narrow density-sensitive formations, significantly improving the cementing quality of ultra-deep high-temperature high-pressure gas wells.