NOVELTY - The biological fertilizer comprises a compound bactericide and a fermentation carrier. The biological fertilizer is obtained by fermenting mixed straws and chemical fertilizers. The compound bactericide is formed by absorbing mixed solution of strains using an adsorption carrier. The fermentation carrier as well as the adsorption carrier is a mixture of crop straws with the chemical fertilizers. An inoculation amount of the compound bactericide in the fermentation carrier is 0.1-0.5 wt.%. A weight ratio of the mixed solution of the strains to the adsorption carrier is 1:2-1:3.    USE - Used as a biological fertilizer.    ADVANTAGE - The biological fertilizer improves the immunity, stress resistance, disease resistance and quality of the agricultural crop, and can be economically prepared with high productivity and quality in an environmentally friendly manner.    DETAILED DESCRIPTION - The biological fertilizer comprises a compound bactericide and a fermentation carrier. The biological fertilizer is obtained by fermenting mixed straws and chemical fertilizers. The compound bactericide is formed by absorbing mixed solution of strains using an adsorption carrier. The fermentation carrier as well as the adsorption carrier is a mixture of crop straws with the chemical fertilizers. An inoculation amount of the compound bactericide in the fermentation carrier is 0.1-0.5 wt.%. A weight ratio of the mixed solution of the strains to the adsorption carrier is 1:2-1:3. The mixed solution of the strains is a mixture of Bacillus stearothermophilus, Bacillus licheniformis, Bacillus megaterium, Nocardia and Bacillus subtilis according to a weight ratio of 0.8-1.2:1.6-2.4:0.8-1.2. The chemical fertilizers are urea, calcium magnesium phosphate and/or potassium sulfate according to a weight ratio of 50-80:20-50:30-70. The crop straws are soybean straws, corn straws, rape straws, rice straws, wheat straws and/or potato vine straws with grain size of 10-30 meshes. An INDEPENDENT CLAIM is included for a method of preparing biological fertilizer.