Abstract:To investigate the different physical and chemical properties of the mixed starch with raw starch.Sweet buckwheat flour and high gluten wheat flour and 30%buckwheat-70%wheat mixed flour has been used as raw material in this article，and the Osbrone separation method has been used to analysis the three kinds of starch particle composition，structure，solubility，swelling power，pasting and thermal properties.The resultsshowed that mixed starch has the worst dense degree，the highest crystallinity，the largest absorb quantity of heat when the crystal disintegration，the most hardest gelatinization properties，the highest enthalpy value and the slowest growth of solubility，swelling capacity in high temperature compared with single starch.There has no significant effect on the particle morphology and starch crystal by mixed.