The invention relates to a preparation method of an active hydrophilic
formaldehyde-free color fixing agent. The preparation method comprises the following steps: S1) stirring concentrated
hydrochloric acid, slowly dropwise adding
tertiary amine, carrying out a heat-preserved reaction, and regulating the pH value of the obtained solution to 3-4 by using
tertiary amine; S2) carrying out heating to45 DEG C, slowly and dropwise adding
epoxy chloropropane, keeping a temperature at 45-55 DEG C, conducting a reaction for 1.0-2.5 hours under a heat preservation condition so as to obtain a homogeneous solution, regulating the pH value, and performing cooling to obtain an
intermediate product; and b) adding the
intermediate product, polyethyleneimine and deionized water into a reaction
bottle, slowly and dropwise adding
epoxy chloropropane while stirring, carrying out a heat-preserved reaction at 20-40 DEG C for 5-7 hours, regulating the pH value to 6-7, and performing cooling to obtain the hydrophilic color fixing agent. The hydrophilic
formaldehyde-free color fixing agent disclosed by the invention has a relatively high cation degree and reactive
epoxy groups, and also has good hydrophilicity and color fixing effect; and after a cotton fabric is subjected to color fixing treatment with the agent, the washing fastness of the fabric reaches level 3-5 and accords with the national regulation that hygroscopicity is within 5 seconds in China, the finishing of a subsequent procedure can be reduced, and the use requirements of printing and
dyeing plants are met.