Water-soluble starch is a kind of low-degree hydrolysis product that is between starch and starch sugar and is controlled. The product has strong hydration power, can be dissolved at room temperature, good humidity viscosity, good carrier function, almost no sweetness or unsweeteness, strong heat resistance, not easy to browning, good emulsification and thickening effect, small hygroscopicity, not easy to agglomerate, good film forming property and other advantages.