Abstract: The paper establishes EDTA titration for the determination of calcium oxide in nickel ores, investigates the effect of nickel, alkalinity, precipitant, interference elements and calcium reagent on titration, and determines the optimal experimental conditions:temperature of 50-60℃, 1 hour aging time and 20 mL saturated ammonium oxalate, with method detection limit of 1%, relative standard deviation of 1.3%-2.1% and recovery of 98.98%-102.6%. With high sensitivity, the method is suitable for rapid determination of calcium oxide in nickel ores.