Gasification kinetics of char is thought as a key factor in designing and operating gasifiers. The widely used present technique, TGA method, is limited in temperature and heating rate ranges. A fluidized bed reactor (FBR) method is described which is suitable for measuring char reactivity at elevated temperatures up to 1873 K by using CO2 as the gasifying agent. It is capable of carbonizing coal samples under various conditions including rapid heating as well as slow heating, and in-situ measuring char gasification rate directly after carbonization. Char reactivity is evaluated from the time variation of CO concentration in the exit gas. The heterogeneous global model, incorporated with the two-phase model, is used to describe the reaction of chars. On the basis of the model, the film mass transfer resistance and the bubble-emulsion mass transfer resistance are calculated and their influence on the measured results is assessed. Proper selection of operating parameters for assuring reasonable measurement is discussed. Data processing methods have been developed to give fundamental, quantitative measurements of char reactivity, allowing direct comparison of reactivity between chars. (C) 2000 Elsevier Science Ltd. All rights reserved.