The invention discloses a method of detecting periclase content in cement clinker and belongs to the technical field of detection of building materials. The method comprises the steps of S01, crushingcement clinker, crushing, and screening to obtain a clinker sample; S02, mixing castor oil and anhydrous ethyl alcohol in a mass ratio of (10-15):1 to obtain a shielding agent; S03, adding 1 part bymass of the clinker sample into 40-80 parts by mass of the shielding agent, and holding the temperature of 50-70 DEG C for 10-20 min; S04, adding 40-60 parts by mass of ammonium nitrate and 150-200 parts by mass of anhydrous ethyl alcohol to the obtained material of step S03, heating at 85-95% to allow refluxing for 1-4 h, performing suction filtering while the temperature is high, washing the precipitate with hot anhydrous ethyl alcohol, and combining the washed precipitate with the filtrate; S05, cooling the filtrate of the step S04 to room temperature, and detecting periclase content by means of complexometric titration difference process. The method herein is suitable for more efficiently separating solid-solution magnesia and periclase, detection results for periclase are more real and accurate, and stability of the cement clinker can be correctly estimated.