As one of the significant properties in char combustion, char reactivity has been widely investigated. However, the previous deactivation kinetic models are unable to predict the char reactivity for different kinds of coals because of (i) the complex components of different coals; (ii) the additional holding process during heat treatment. In this study, the char reactivity under different heating rates was studied by a self-developed two-step fluidized bed reactor. The char deactivation model is proposed and applied in Carbon Burnout Kinetics (CBK). The results show that char tends to a higher reactivity under a high heating rate, and increasing holding time at the terminal temperature would further decrease char reactivity. Predicting results of char deactivation model are close to experiment results, indicating that this model has a good predicting ability. After applying this model to CBK, modified-CBK (M-CBK) has a better predicting performance for different kinds of coals in char combustion.