The carboxymethylation reaction of cellulose using phase transfer catalyst and chloroacetic acid and the mechanism of alkalization etherification of carboxy Me cellulose were studied.The effects of catalyst, sodium hydroxide concentration and dosage, and etherification time on the viscosity of CM-cellulose sodium solution were investigated.Substitution degree of CM-cellulose sodium and viscosity of 2% solution was measured under different conditions.At alkalization temperature 30-35 degree, alkalization time 50 min, etherification temperature 70-75°, etherification time 70 min, NaOH concentration 25%, catalyst dosage 3%, the viscosity was up to 600-650 MPa·s, substitution degree was 0.530-0.560.