Modified starch is the use of physical, chemical and enzyme means to change the properties of natural starch to meet the needs of applications in all walks of life. The amount and scope of modified starch are very wide. China has produced pregelatinized starch, acidified starch, oxidized starch, etherified starch, esterified starch, cross-linked starch, grafted starch, etc. There are more than 70 varieties in petroleum, medical, construction, agricultural feed, daily chemical and other industries. Among them, the application amount in the paper industry is the largest, accounting for about 50-60% of the total, mainly used as wet end additives, interlayer or surface sprays, surface sizing agents and coating adhesives. They significantly improve various physical strengths of paper, improve quality and grade, reduce wood pulp ratio, improve retention rate of fine fibers and fillers, improve ash content, whiteness and opacity of finished paper, reduce wet end breakage, reduce Three waste discharge, and improve printing performance.