The aim of this study is to establish a dehydration model that is able to calculate the water release of cement paste at elevated temperature. The main hydrates in ordinary Portland cement paste (C-S-H, portlandite, aluminates and sulfo-aluminates) were modelled separately and then combined to form the model of the cement paste. In this way, the model is able to predict the dehydration of cement pastes with different compositions without re-fitting. For each hydrate, the dehydration law takes account not only of the maximum quantity of water that can be released at each temperature but also of the kinetics to reach that equilibrium. The model is thus able to reproduce the paste dehydration for any heating rate. Thermogravimetric tests were carried out with different heating rates to validate 2 Jin WANG et al. the model in comparison to experimental results from the literature. The results demonstrated the capability of the model in different situations.