Desalting the sodium chloride from water solution of 9-aminopelargonic acid by elec-trodialysis．using “Permaplex”C-20 and A-20 ion-exehange membranes has been studied．Experiments indicate the following operating conditions to be the optimum for a bulk solution containing 3.5 gm of 9-aminopelargonic acid and 1.5 gm of sodium chloride in 100 ml of the solution：1． pH value of the solution in central conpartment=7.5--7.8；2．Maximum current density=about 8 mA／cm2；applied voltage=65 V；3．Concentration of anolyte一sodium hydroxide=0.00135±0.0002 N，and concen-tration of catholyte-hydrochloride acid=0.0040±0.0002 N：4．Electrodialysis is stopped when the specific conductivity of the solution reaches to 5×10-3Q-1cm-1．After desalting the sodium chloride by electrodialysis，9-aminopelargonic acid was crystalized twice from water to give the pure product，mp．186—189℃，ash content 0.1％，chloride ion trace．The yield is about 93％．