Sodium carboxymethyl starch, also known as carboxymethyl starch, is an anionic starch ether with the chemical formula of [C10H19O8Na] n. It is a white or yellow powder and an electrolyte soluble in cold water. It is a kind of modified starch, belonging to ether starch, and is a water-soluble anionic polymer compound. It is tasteless, non-toxic, not easy to mildew, and soluble in water when the degree of substitution is more than 0.2.