Abstract: The improved preparation method for carboxy methylation of konjac glucomannan (KGM) was proposed in this paper according to molecular structural characteristics of KGM. Carboxymethyl konjac glucomannan (CMK) was prepared by blending konjac glucomannan with etherification agent firstly and then basifying and catalyzing in ethanol. Through single factor and orthogonal experiments, the effects of reaction conditions on degree of substitution (DS) and apparent viscosity (η) were investigated, and the optimum reaction conditions were obtained as follows: 55℃, pH 12 for 3 hours. The results indicate that the maximal values of DS and η were 0.5278 and 15.57 Pa·s, respectively. The reaction mechanism for carboxy methylation of KGM was proposed and checked by infrared spectra. Meanwhile, it also shows that the properties of CMK are rather good in terms of hydrated rate and hydrosol transmittance.