Phase change materials (PCMs), an innovative class of functional materials, exhibit the ability to store or release thermal energy through reversible transformations at specific phase transition temperatures, which have been extensively employed in aerospace, military, construction, and refrigeration industries. As oil and gas exploration and development word-widely advance into deeper formations, extremely high-temperature and high-pressure conditions in these environments impose significant challenges on drilling fluids and down-hole instruments, limiting the progress of deep hydrocarbon exploration. To address the technical challenges related to the high-temperature resistant stability of drilling fluids in deep formations, this study investigates the integration of PCMs into drilling fluids. Through theoretical analysis and experimental simulations, the feasibility of utilizing the "phase change heat storage principle" of PCMs to reduce circulating drilling fluid temperatures in boreholes was demonstrated. The results indicate that three selected PCMs exhibit phase transition temperatures in the range of 120–145℃ and phase change latent heat of 90.3–280.6 J/g, showcasing excellent phase change heat storage properties. The materials were found to be compatible with drilling fluids. At a PCM concentration of 12%, the rheological and filtration properties of the drilling fluids still met operational requirements. Incorporating PCMs into drilling fluids effectively reduced the circulating temperature in boreholes, with a more pronounced cooling effect observed at higher PCM concentrations. At a concentration of 12%, the circulating temperature of drilling fluids was reduced by up to 20℃. Additionally, the PCMs demonstrated good reusability, consistently undergoing the "heat storage and release" phase change process, thereby satisfying the circulating cooling demands of drilling fluids. The findings provide a robust reference for PCM integration in high-temperature drilling fluids, particularly in ultra-deep wells with extreme thermal conditions.