The invention discloses a method and a special bacteria-adding equipment for adding bacteria after preparing bio-organic fertilizer. When the bio-organic fertilizer is being produced, the water content is 25-30% during the granulation process; after the granulation, the high-temperature quick drying is adopted in a drying cylinder and the water content is not more than 5%; after drying and cooling by a cooling cylinder, a microbial inoculum is added before packaging; furthermore, the special bacteria adding device is adopted to carry out high-pressure haze spraying so as to carry out computation adding; subsequently, the post-procedure of bacteria adding is carried out and the special bacteria adding equipment is selected; the bacterial liquid is added so that the active bacteria number is kept at 2 billion / gram; and before the product is packaged, the humidity needs to be kept at 12% of the water content by mass percentage, thus leading the selected bio-organic fertilizer grains to keep uniform and leading moisture to keep in an environment needed by the added microorganism bacteria. The method effectively avoids the loss of the active bacteria number of the beneficial bacteria in the bio-organic fertilizer, ensures the active bacteria number of the beneficial bacteria during adding the bio-organic fertilizer, and leads the beneficial bacteria to bring beneficial functions tothe bio-organic fertilizers.