Method for testing content of magnesium oxide in magnesium oxide expanding agent

The invention provides a method for testing the content of magnesium oxide in a magnesium oxide expanding agent. The method comprises the steps of: enabling a magnesium oxide expanding agent sample to react in a buffer solution with the pH value of 13.0, and detecting the content of the magnesium oxide in the magnesium oxide expanding agent sample, wherein a sodium hydroxide aqueous solution is used as the buffer solution. According to the invention, the influence of a magnesium element in undecomposed magnesite and the magnesium element in generated magnesium hydrate partially absorbing moisture in the magnesium oxide expanding agent can be eliminated, the influence of the calcium oxide in the magnesium oxide expanding agent can be effectively eliminated, and the measured content of the magnesium oxide is the effective content of the magnesium oxide capable of reacting with water; and a test result is capable of truly reflecting the reaction capacity of the magnesium oxide expanding agent in a cement concrete hydration environment, and is closely related to the expansion priority of the magnetism oxide expanding agent in cement concrete.