A new technique combining ion-exchange membrane with potentiometrio titration was used to determine microquantity of Ce⁴⁺ in silicate glass.It extends conventional potontiometrio titration to microquantitalive determination.The derermination oan be carried out at 10^-6 N concentration, and the lower limit is down to 1 μg.This method is simple and rapid, and the average deviation is less than 1%.Rapid decomposition of silicate glass is achived in a specially designed sealed vessel made of polytetra,fluoro-ethylene to avoid contamination and the possible oxidation of sample in hydroftuorio acid at 110℃.