The invention discloses a special composite organic fertilizer for mangnolia officinalis and a preparation method of the special composite organic fertilizer, wherein the special composite organic fertilizer for mangnolia officinalis consists of the following ingredients in parts by weight: 10 to 20 parts of soybean meal, 30 to 40 parts of plant straws, 10 to 13 parts of cabbage slag, 0.5 to 2 parts of composite strains, 15 to 20 parts of potassium sulfate, 0.3 to 0.8 part of manganese sulfate, 0.4 to 0.9 part of ferrous sulfate, 10 to 25 parts of ammonium sulfate, 2 to 5 parts of borax, 10 to 15 parts of diammonium phosphate, 2 to 5 parts of fulvic acid, 1 to 4 parts of soluble chitosan, 2 to 5 parts of trace boron ore, 0.04 to 0.08 part of dipterex, 0.03 to 0.05 parts of chlorothalonil and 25 to 32 parts of filling materials. According to the growth rule of the mangnolia officinalis, the fertilizer provided by the invention adopts a great number of biological organic nitrogenous fertilizers, the physical properties of the soil can be obviously improved after a great number of fertilizers are utilized, the effective void content of the soil is increased, and the survival rate of the young seedlings of the mangnolia officinalis is improved.