The Purpose of this study is to tinvestigate the characteristics of CMC prepared from Viscose Rayon. Especially we prepare CMC as the parameter about reaction time, temperature, concentration and measures water solubility & the degree of substitution (D.S.) of CMC. Carboxymethylation conform to common method using NaOH in mercerization and monochloracetic acid in etherification. The water solubility of CMC shows higher influence about concentration of NaOH solution, concentration of monochloracetic acid.