Fly ash has been widely used as supplementary cementitious materials in concrete industry.Hydration mechanism of fly ash-blended cement is much more complicated due to the mutual effect of cement hydration and fly ash reaction.In this paper, the hydration heat evolution rate and cumulative hydration heat of blended cement containing 0, 20%, 35%, 50% and 65% of fly ash were measured at 298 K, 318 K and 333 K with an isothermal calorimeter.Based on the hydration kinetics model, three hydration processes, namely nucleation and crystal growth (NG), interactions at phase boundaries (I) and diffusion (D) were characterized, the relationship between the hydration rate and hydration degree was discussed at different stages, kinetics parameters, n, K, and Ea, were calculated and analyzed.Results indicated that the hydration evolution rate and cumulative hydration heat of blended cement decrease with increasing the replacement ratio of fly ash.Elevated temperatures promote the hydration process, especially for blended cement containing high amount of fly ash.The kinetics model could simulate the hydration process of blended cement containing no more than 65% of fly ash, whose hydration process sequence is NG→I→D at 298 K and 318 K, but it becomes NG→D at 333 K.The simulation error has a little increase with increasing fly ash content and temperature.The value of Ea for NG process is nearly three times as large as that for D process.The value of Ea for the overall reaction of blended cement increases with increasing the replacement ratio of fly ash.