Starch ether is etherified starch, which is a starch substituted ether formed by the reaction between hydroxyl groups in starch molecules and reactive substances. Including hydroxyalkyl starch, carboxymethyl starch, cationic starch, etc. Because the etherification of starch improves the viscosity stability, and under strong alkaline conditions, the ether bond is not easily hydrolyzed, so etherified starch can be used in many fields. In the mortar industry, it has the functions of rapid thickening, improving the sag resistance of materials, prolonging operation time, improving water retention, etc., and has good compatibility with other materials.