The invention relates to a conditioner used for protecting oil, which comprises a main material and auxiliary materials, wherein the main raw material comprises medical stone and the auxiliary materials comprise potassium chloride, magnesium oxide, zinc sulfate and the like. The conditioner has a special medical function to the soil and extremely strong hydrophilic capacity and adsorbability, caninhibit volatilization and loss of nitrogen in the soil through absorption, effectively activates fixed phosphorus and potassium nutrients in the soil, promotes the growth of microorganisms and the utilization rate of the nutrients by the crops, can adsorb sodium and chlorine ions in saline-alkali soil, improves the soil property and neutralizes the pH value, has a dual-regulation function, and protects fertilizers and beneficiates the effects. In addition, the conditioner can adsorb heavy metals of lead, arsenic, cadmium and harmful elements and the like in the soil and prevent the heavy metals and the harmful elements from being absorbed by the crops, effectively kills the harmful bacteria in the soil, and prevents agricultural products from absorbing and leaving harmful substances, thereby enhancing the organic matters in the soil, being beneficial to the plant growth and improving the yield.