The acid-catalysis of chromic acid oxidation of carboxymethyl cellulose (CMC) as a polysaccharide in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated spectrophotometrically. The experimental results showed first-order kinetics in chromic acid and fractional first-order dependence with respect to [CMC]. A kinetic evidence for the formation of 1:1 complex between chromic acid and CMC was revealed. The hydrogen ion dependence of the reaction rates showed that the oxidation process is acid-catalyzed. Induced polymerization of acrylonitrile indicated that the oxidation process proceeds by free-radical mechanism. The kinetic parameters have been evaluated and a tentative reaction mechanism consistent with the kinetic results is suggested.