The invention relates to a protective oil, and particularly relates to a protective oil for lead-acid storage battery terminals and a preparation method thereof. The protective oil is prepared from the following components by the weight percentage: 20-40% of vaseline, 20-40% of molybdenum disulfide, and 20-40% of an anti-corrosion oil, wherein the total content is 100%. The invention aims to provide the protective oil for the lead-acid storage battery terminals and the preparation method thereof, and solves the terminal corrosion problem.