Abstract: The migration behavior of alkali metals during co-gasification of cornstalk and PE in a fixed bed at different temperatures was studied on the thermodynamic equilibrium calculation, the X-ray power diffraction and scanning electron microscope/energy dispersive spectrometer. The results indicat that the alkali chlorides (KCl、K₂Cl₂、NaCl)are the main components in gaseous. There is a large amounts of C and H in the fules with the mixed of plastic PE. The H makes the Cl prefer HCl to KCl, meanwhile, the release radio of K is lower than the cornstalk gasification cause of the C easily reacted with K than Na. Alkali metal compounds in ashes are mainly in the forms of KCl, NaCl, K₂SO₄, KAlSi₃O₈, KAlSiO₄, NaAlSi₃O₈, NaAlSiO₄. The KCl,NaCl begin to release when the reacting temperature above 800℃ and most of K,Na,Cl are easily deposited on the edge of the hole.