Compound modified starch prepared by four modification methods

The invention provides a process for preparing compound modified starch. The compound modified starch is obtained by starch modification through cross linking reaction, carboxymethyation reaction, hydroxyalkylation reaction and pre-gelatinization reaction; is advantageous in good performance, stable viscosity, rapid solution in cold water, good water-absorbing capability, strong re-hydration property, shear resistance, acid resistance and salt/alkali resistance; and has the characteristics of higher freezing stability and freeze/thawing stability, no flocculation or deposition and good film-forming property. Besides, the process can manufacture products with different performances by adjusting the quantity of auxiliary ingredients and adjusting the sequence of reactions, and has good application prospects in the fields of building mortar and coatings, petroleum drilling, textile printing and dyeing and the like.