The invention relates to the technical field of soil conditioners, in particular to a biomass charcoal soil conditioner containing biological stimulant and a preparation method of biomass charcoal soil conditioner. The biomass charcoal soil conditioner is prepared from 20-40 parts of biological stimulant, 10-30 parts of active calcium, 5-10 parts of alkali residues, 5-15 parts of plant ash and 10-20 parts of biomass charcoal; the active nano calcium and the biological stimulant can directly reach cells of crops, and the effect of increasing the yield is remarkable; the biomass charcoal has high aromatization degree, large specific surface area, well-developed pore structure and various organic functional groups, and has strong adsorption capacity for heavy metals. To sum up, the soil conditioner adopts the five substances, namely, the biological stimulant, the active calcium, the alkali residues, the plant ash and the biomass charcoal to cooperate with one another, finally, it is realized that acid soil can be improved rapidly, the soil permeability can be effectively improved, soil hardening is avoided, heavy metal contaminated soil is repaired, soil microbial activity is promoted, the ability of soil to maintain water and a fertilizer is enhanced, the consumption of the fertilizer is reduced, the utilization rate of the fertilizer is increased, and the effect of increasing the yield of the crops is remarkable.