The invention discloses a soil conditioner for reducing the content of heavy metals in soil, wherein the soil conditioner comprises the following components according to parts by weight: 20-30 parts of calcium hydroxide, 15-25 parts of superphosphate, 2-8 parts of magnesium sulfate, and 40-60 parts of clinoptilolit. The invention further discloses a preparation method of the soil conditioner. The preparation method of the soil conditioner is made on the basis of relevant tests and the practical production and application effects of flue-cured tobaccos, and takes both use cost and use efficiency into consideration. The method is simple in operation, low in cost, easy in popularization and remarkable in effect, the tobacco quality is improved on a certain degree, and the content of heavy metals in the tobacco is also reduced. The mechanism of action of the method is clear, scientific and reasonable.