The invention relates to the technical field of biological fertilizers, in particular to a biological organic fertilizer and a method for preparing the same. The biological organic fertilizer is mainly made of raw materials including, by weight, 50-80 parts of animal feces, 40-60 parts of crop straw, 10-25 parts of wheat bran, 5-20 parts of peanut bran, 10-30 parts of rice bran, 10-25 parts of biogas residues, 15-30 parts of plant ash, 2-10 parts of brown sugar, 1-5 parts of microbial nutrient solution and 1-10 parts of starter culture. The biological organic fertilizer and the method have the advantages that soil properties of soil can be improved, the resource utilization rates can be increased, and the biological organic fertilizer and the method are environmentally friendly and are free of pollution; abundant balanced nutrition can be provided for crops, accordingly, the yield of the crops can be effectively increased, and the quality of the crops can be effectively improved.