The paper develops a low-heat and early-strength cementing slurry based on a homemade phase change microcapsule admixture to reduce the effect of exothermic cement hydration on hydrate stability during the cementing process. The microcapsules were prepared using poly (methyl methacrylate) encapsulated with mixed alkanes. Various tests were conducted to determine the properties of the microcapsules themselves and their effects on the heat of hydration and compressive strength of the cement slurry/stone. The results showed that the phase change temperature of the microcapsules ranged from 5.57°C–16.52°C, the enthalpy of phase change was 111.55 J/g and the encapsulation efficiency was 48.9%. The cementing water slurry compounding experiments demonstrated that Micro-P1 had a small effect on the flowability of cement slurry, and was able to improve the early compressive strength of cementite by 40.3% and reduce the rate of exothermic hydration of cement slurry by 40%. Micro-P1 has been shown to improve the success rate of cementing in hydrate-bearing formations.