The method for determination of periclase content in MgO expansive agents ( MEA ) based on extraction of periclase with ammonium nitrate-glycerin ethanol were proposed. The effects of magnesium-bearing minerals such as brucite,magnesite,magnesite tailings,dolomite,and serpentine on the accuracy for analysis of periclase content in MgO expansive agents were evaluated.Results showed that periclase in MgO expansive agents would be accurately measured by extraction with ammonium nitrate-glycerin ethanol. The recovery of periclase was between 98. 14％ and 100. 40％. Impurities such as magnesite,magnesite tailings, dolomite,and serpentine had no significant effects on the measured content of periclase.Little influence on the measured periclase content was observed with brucite less than 20％,but the measured periclase content could deviate significantly from the true value with bruciteis between 25％ and 50％.