Abstract: The transformation of potassium during pyrolysis and gasification was studied in a fixed bed. The effects of potassium based catalyst on the steam gasification reactivity and the transformation of potassium were investigated by TG-DSC. Results show that all the potassium carbonate loaded by either impregnation or mechanical mixing has a marked catalytic effectiveness. The reactivity of Shenfu char increases with potassium loadings up to a saturation loading of about 10%. The catalytic effect has a maximum value. The transformation of potassium and the amount of potassium intermediate have been confirmed during pyrolysis and gasification. And the reactivity of chars depends on the amount of potassium intermediate. Potassium carbonate has an obvious catalytic effect, and potassium chloride has a poor catalytic effect. However, the catalytic effect of potassium sulfate increases obviously with the increasing of temperature in the range of 700～800℃.