Abstract: PCDD/Fs in fly ash from bag filters of different type of incinerator were detected by high resolution gas chromatography coupled with low resolution mass spectrometry(HRGC/LRMS). The results show the types of fuel and chlorine content in fly ash have remarkable influence on concentration of PCDD/Fs in fly ash. There is a direct proportional correlation between PCDD/Fs and chlorine content in fly ash. Although large amounts of heavy metals are found in fly ash, they do not have a noticeable relationship with dioxins in fly ash. The congener profiles of dioxins in fly ash are different between the fluidized bed incinerator and stoke grate incinerator. The major homologue of PCDD/Fs is 1,2,3,4,6,7,8-HpCDD，1,2,3,4,6,7,8-HpCDF and OCDD. The TEQ of PCDFs is higher than that of PCDDs. The primary study shows that the concentration of dioxins in fly ash and toxic equivalent quantity(TEQ) from the stoke grate incinerator are higher than those of fly ash from the fluidized bed incineration.