The invention discloses organic-inorganic compound biological medicine fertilizer special for lobsters and a preparation method thereof. The organic-inorganic compound biological medicine fertilizer special for lobsters is made with, by weight, 50-65 parts of chicken manure, 20-25 parts of greenhouse waste, 10-15 parts of straw powder, 15-20 parts of fruit residue, 10-12 parts of bone meal, 0.1-0.2 part of bacillus subtilis, 0.1-0.2 part of aspergillus oryzae, 0.1-0.2 part of brewer's yeast, 3-6 parts of pomegranate peel, 2-4 parts of azadirachtin, 5-7 parts of root and rhizome of Japanese climbing fern, 5-7 parts of betel nut, 3-6 parts of copper sulfate, 12-14 parts of potassium sulphate, 12-14 parts of ammonium bicarbonate, 10-12 parts of calcium superphosphate, and 10-14 parts of urea. The organic-inorganic compound biological medicine fertilizer is fermented; Chinese herbal decoction functioning in killing insects is added; accordingly, water quality is improved, dissolved nutrients are increased, immunity and disease resistance in lobsters are enhanced, diseases are reduced effectively, and lobster yield is increased.