The invention discloses a preparation method of 
carboxymethyl starch used for 
reactive dye printing. 
Starch is taken as a main 
raw material, a compound modification technology is adopted, different modification reactions are successively completed in 
slurry taking a mixed 
solvent as a reaction medium, and finally the 
carboxymethyl starch is generated. The preparation method comprises the following steps: firstly dispersing 
starch in the mixed 
solvent containing ethyl 
alcohol and 
isopropyl alcohol, adding alkaline liquor for carrying out low temperature alkalization, then adding an etherifying agent for carrying out high temperature etherification, then adding a crosslinking agent at a certain temperature for carrying out micro-crosslinking, after crosslinking reaction is finished, washing, 
drying, and smashing, so that the 
carboxymethyl starch is obtained. The preparation method disclosed by the invention has the advantages that the mixed 
solvent is adopted in the technology, so that carboxymethylation reaction of the 
starch can be promoted, and substitution uniformity of the product is improved; the 
starch is subjected to low temperature alkalization, so that starch pasting can be effectively prevented, and the 
solubility and transparency of the product are improved; high temperature etherification can promote the 
permeation effect of feed liquid to the starch, and the 
reaction rate is accelerated; and micro-crosslinking can improve the structural 
viscosity and 
salt resistance of the product to a certain degree. The carboxymethyl starch product can completely replace 
sodium alginate.