The invention relates to a biological composite fertilizer, and concretely relates to a biological composite fertilizer. The biological composite fertilizer is characterized by being composed of the following raw materials: 7-9 parts of a microbial composite inoculant, 3-5 parts of nitrogen-fixing bacteria, 3-5 parts of phosphobacteria, 3-5 parts of potassium bacteria, 5-15 parts of humic acid, 10-20 parts of amino acids, 4-6 parts of chitin, 1-3 parts of polypeptide, 5-15 parts of medium and trace elements, 5-15 parts of an algae fertilizer, 8-10 parts of zeolite powder, and 1-3 parts of a synergist. The fertilizer is capable of obviously improving soil fertility and microbial environment in soil, and has effects of resisting insect diseases. The fertilizer is low in cost, simple in production technology, long in fertilizer efficiency and free of pollution. Nutrition balance is reached through scientific reasonable formula, nutrients demanded by crop growth are satisfied, large-molecular natural organic compounds are accelerated to be decomposed into an organic fertilizer by adding the inoculants, organic pollutants are decomposed, the capability of crop absorbing nutrients is effectively improved, fertilizer waste is reduced, damage of chemical fertilizers to soil is reduced, and thus nutrition balance is realized, nutrients demanded by crops are satisfied, and economic benefit of crops is improved.