Hydroxyl radical produced by H₂O₂/Fe^2＋ was assayed by the new method.After oxidized by hydroxyl radical the A₅₃₆ of 1, 10-phenanthroline-Fe^2＋ decreased apparently.The △A₅₃₆ was dependent upon the dosage of 1, 10-phenanthroline, FeSO₄ or H₂O₂ individually. The △A₅₃₆ increased as the reaction lasted. It was demonstrated that the hydroxyl radical scanvenge effect of mannitol, ascorbic acid and thiourea was dosedependent by the new method.