The invention relates to charcoal for tobacco field soil improvement and a preparation method of the charcoal, and belongs to the technical field of agricultural fertilizers. The charcoal for tobacco field soil improvement comprises a production raw material of distillers' grains. The preparation method specifically comprises the following steps: performing mixing fermentation on one or more raw materials of sorghum, rice, sticky rice, wheat, corn and the like to brew wine; putting obtained distillers' grains into a calcining furnace for calcining so as to obtain a calcined product; performing water spraying washing on the obtained calcined product, thereby obtaining a charcoal product. As the distillers' grains are adopted as a raw material, and a specific preparation method is utilized, the obtained product is good in practicability, high in carbon content and rich in trace nutrient element, the yield of tobacco can be effectively increased, the quality of the tobacco and the fertilizer utilization efficiency can be effectively improved, the physical and chemical properties of soil of a tobacco field can be remarkably improved, the ratio of carbon to nitrogen in the soil of the tobacco field can be remarkably increased, the soil porosity can be improved, the soil capacity can be reduced, the maximum water-holding capacity of the soil can be increased, the microorganism environment of the soil can be improved, and in the application process, the charcoal is applied together with a base fertilizer for planting the tobacco, so that the labor is not increased.