Method for preparing starch polysaccharide iron by acid complexing process

The invention relates to the field of fine chemical engineering and feed additives, in particular to a method for preparing starch polysaccharide iron by an acid complexing process. The preparation method comprises the following steps: degrading starch by using a hydrochloric acid solution to obtain a starch polysaccharide solution with relatively small molecular weight, oxidizing starch polysaccharide by using an alkali solution and a hydrogen peroxide solution to prepare an oxidized starch polysaccharide solution, complexing under an acidic condition to obtain a starch polysaccharide iron solution, and carrying out ultrafiltration impurity removal and spray drying to obtain the iron-rich starch. The hygienic index chromium content of the prepared starch polysaccharide iron is lower (less than or equal to 5mg/kg), so that the requirement of a feed additive on the index is met; the prepared starch polysaccharide iron has better solubility in drinking water (1.5 g of the product can be dissolved in 30 ml of dr