It was studied that the process and mechanism of potassium extraction from the potassium-rich shale sample during roasting via SEM, XRD and thermal analysis (TG and DSC). The result of roasting test shows that roasting size has a little affect on ratio of potassium extraction, however, the effect of roasting temperature, roasting time and mNaOH:mshale on potassium extraction is significant. Under the optimum conditions, the ratio of potassium extraction is more than 88 %. SEM, XRD and thermal analysis shows that, during roasting, NaOH contributes to decomposition and melt of the minerals like potassium feldspar and muscovite in the sample and intact structure of minerals in the shale are broken down gradually and there are new crystal phases like kalsilite in the roasting products. Under alkali conditions, increasing roasting temperature promotes decomposition of silicate and aluminosilicate minerals.