The present study aims to provide basis for the temperature and crack control of mass concrete by investigating the difference of hydration heat between low-heat Portland cement and mineral-mixed cementitious material. Firstly, the processes of hydration heat release in low-heat Portland cement and mineral-mixed cementitious material were determined via direct method. According to the calculated hydration heat release curve and hydration rate curve, the differences between the two in terms of hydration law were analyzed. Furthermore, the hydration processes were characterized by the integral equations of Krstulovic-Dabic model in three stages and the differences in the process of hydration were further studied. Research results show that in the early stage of hydration, the hydration heat of cementitious material with slag was lower than that of low-heat Portland cement, but was higher than that of low-heat Portland cement in the later stage; compared with those of low-heat Portland cement, the initial and final setting time was delayed and the accelerating period and the deceleration period was prolonged by adding a certain amount of mineral admixture. In addition, in nucleation and crystal growth period (NG), hydration resistance increased as the n value became larger, and the initial setting time was delayed; as the k_NG value climbed, rate of hydration increased and the acceleration period shortened, so that the final setting time was in advance; while in the phase boundary reaction period (I) and diffusion period (D), the greater values of k_I and k_D, the faster hydration speed and the longer deceleration period would be.