A magnesium halide solution is disclosed. The magnesium halide solution comprises a magnesium halide, an oxygen-containing organic titanium compound, a hydroxyl-containing compound, and an organic solvent. The magnesium halide solution further comprises an organic heterocyclic compound. The organic solvent is a hydrocarbon and/or a halogenated hydrocarbon. The organic heterocyclic compound is at least one selected from a group consisting of a sulphur-containing organic heterocyclic compound, a nitrogen-containing organic heterocyclic compound, and an organic epoxy compound. The magnesium halide solution has a good stability, and can be used for preparing a catalyst for olefin polymerization and copolymerization reactions. The raw material of the magnesium halide solution is cheap and easy to be obtained. The preparing method is easy to be performed and is environment-friendly.