The fusion process of ash samples respectively with high and low ash fusion point was observed under reducing atmosphere with the Xray absorption fine structure (XAFS) spectrum of Shanghai Synchrotron Radiation Facility (SSRF). Results show that during fusion process, the valence state of Fe changes from Fe3+ to Fe2+; for ash samples with high fusion point, the conversion generally happens at the temperature ranging from 900 ℃ to 1 300 ℃, with a Fe transition from tetrahedral to octahedral coordination; whereas, for those samples with low fusion point, tetrahedral Fe forms firstly, which transforms to octahedral Fe later on; these morphology changes happen before fusion process; for ash samples with low fusion point, significant changes are observed in FeO structure of the firstlayer coordination at the moment of complete fusion, while those with high fusion point, no evident change is observed in the coordination structure.