The invention belongs to the field of microbial fermentation and provides a preparation method of a fertilizer special for leaf vegetables. The preparation method uses poor fruits, dropped fruits, fruit residues, fruit and vegetable straw and other waste produced in the agricultural production as raw materials, mannitol, magnesium sulfate and zinc sulfate are added in secondary fermentation in a cooperating mode, the demands for nitrogen, phosphorus and potassium are balanced in the growth process of the leaf vegetables, and medium trace elements and especially magnesium and zinc can promote synthesis and photosynthesis of chlorophyll and have the obvious effect on the leaf vegetables. In addition, the microbial action of the special fertilizer reduces the nitrite content, nitrate nitrogen is converted into ammonium nitrogen, and absorption and utilization of leaf vegetables are promoted.