The formation and migration of dioxins were investigated by analyzing the distribution characteristics of dioxins in all output products from a updraft fixed bed gasifier for disposing domestic solid waste.The results show that after the purification of the wet scrubbing coupled with an electric tar precipitator,the content of dioxins in the flue gas of the gasifier output is 0. 48ng I-TEQ/Nm 3 ,and the contents of dioxins in the scrubbing water and the tar are higher,which are respectively 8259. 50ng I-TEQ/L and 5941. 84ng I-TEQ/kg,and that the total emission factor of dioxins in the gasifier system is 165. 86μg I-TEQ/t,of which 96. 06% is emitted by the residual,3. 58% by the tar,and only 0. 35% is discharged with the flue gas.Therefore,the residue is the main emission resource of dioxins,which is obviously different from the municipal solid waste incineration.The similar distribution characteristics of dioxins in the residues,the scrubbing waste,the tar and the flue gas indicate that dioxins are generated in the gasifier chamber rather than the process of flue gas cleaning.Thus,it is suggested that the effective control of the generation of dioxins within the gasifier chamber is the key when the updraft fixed bed gasifier is used to dispose solid waste.