The advancements in study on formation mechanisms of dioxin in municipal solid waste （MSW） incinerators have been completely presented. Studies show that the de novo synthetic reaction and the outphase catalytic reaction of the precursors are the must major ones for formation of dioxin. The influence factors include temperature

flue gas atmosphere of said reactions

oxygen content

chloride source

and catalysts etc.. Regardless of which nonhomogenous reaction occurred

it can be considered as outphase catalytic reaction on the surface of fly ash. In order to control and reduce the formation and emission of dioxin from MSW incinerators

the said main affecting factors should be set about.