Abstract: To investigate the variation in gasification reactivity and microstructure of char from the multi-circulation fluidized bed gasifier, 3 chars from different rank coals were gasified in a simulated multi-circulated reactor (rapid heating-up fixed bed). The carbon conversion was calculated from the weight of residues, and the structure was analyzed by pore and XRD analyzer. The results show that with the increase of cycle time, the carbon conversion of low rank HLH lignite char increases while that of SM bituminous and JC anthracite chars decrease. The evolutions of BET surface area and micropore area have a peak value with the circulate time. The variation of graphitization is similar with the carbon conversion, which can be considered as the key factor to determine the carbon conversion.