Abstract: Zirconium in rare earth-magnesium-zirconium master alloy was determined by EDTA titrimetry.Series of experiments were performed to investigate the decomposing method,titration acidity and temperature.Interferences of matrix and impurities were analyzed and the removal steps were proposed.The relative standard deviation was less than 2.5 % and the recovery rate by standard addition method was in the range of 98.9 %~101.8 %.