Preparation method of modified amino-containing water-insoluble polymer

The invention discloses a preparation method of a modified amino-containing water-insoluble polymer in the technical field of modification of amino-containing water-insoluble polymers, and the preparation method comprises the following steps: adding a chemical modifier into an amino-containing water-insoluble polymer solution, stirring, and carrying out a chemical reaction to obtain the modified amino-containing water-insoluble polymer, wherein during stirring, it is ensured that the temperature is higher than the solidification temperature of the amino-containing indissolvable polymer solution, and the modifier is added into the amino-containing indissolvable polymer solution which is a solution of amino-containing indissolvable polymer combined with weak acid radical ions; the modifier is a substance with groups capable of chemically reacting with amino groups in the amino-containing insoluble polymer, and the molar weight of the modifier is smaller than that of the amino groups in the amino-containing inso