In this study, a microcalorimeter was used to analyze the hydration heat of cement pastes with different contents and fineness of limestone powder. Based on the Krstulovi?-Dabi? model, the actual hydration reaction rate curve and the theoretical hydration reaction rate curve of each stage were obtained. The reaction kinetics related parameters including degree of reaction, reaction order, and reaction rate constants for the NG, I, and D stages were calculated to analyze the influence of limestone powder content and fineness on cement hydration. Experimental results demonstrate that within the limestone powder dosage range of 0~35% and specific surface area of 465 m2/kg ~665 m2/kg, the correlated increase in both parameters enhances cement hydration kinetics, resulting in both elevated hydration heat peaks and accelerated peak occurrence. When the limestone powder content is 35%, the peak increases by 26.2% and occurs 3.17 hours earlier. Additionally, the reaction degree of the NG process (crystallization nucleation and crystal growth process) of cement hydration increases. The addition of limestone powder and the increased fineness enhance the early hydration reaction rate, while leading to a limited hydration degree in the later-stage.