The invention relates to a preparation method of special bottom fertilizer for litchis, in particular to a preparation method of special biochemical-humic-acid-containing bottom fertilizer for litchis. The preparation method is characterized by including the steps that decomposed organic fertilizer, supernate and chelated micro and medium fertilizer liquid are prepared, urea, potassium sulfate and monoammonium phosphate are mixed and smashed to pass through a sieve of 100-200 meshes to obtain nitrogen phosphorous and potassium mixed fertilizer, the chelated micro and medium fertilizer liquid and the obtained nitrogen phosphorous and potassium mixed fertilizer are mixed evenly and sprayed into an obtained decomposed organic fertilizer and stove ash mixed material for granulation, and finally wintergreen oil is sprayed for enveloping to obtain the special bottom fertilizer for the litchis. The special bottom fertilizer can loosen soil, stimulate physiological metabolism of plants, promote rooting of the litchis, improve adverse stress resistance of the litchis and reduce plant diseases and insect pests, and the fertilizer absorption efficiency and fruit quality are improved.