In this article, carboxymethyl starch (CMS) with a high degree of substitution (0.91) and a high viscosity was synthesized by optimized reaction conditions, and its structure and surface morphology were analyzed by IR spectroscopy and scanning electron microscopy. The results of this application study show that CMS exhibited excellent printing behavior. CMS could substitute for 60% sodium alginate when it was used as a thickening agent in the printing paste of reactive dyes; therefore, the cost was greatly reduced. (C) 2003 Wiley Periodicals, Inc.