The invention relates to a preparation technology of a slow-release potassium fertilizer capable of increasing the potassium content of tobacco leaves and including microorganisms. The preparation technology comprises the following steps of preparing a fermentation raw material: (a), mixing the following components in percentage by weight of 50-75% of potassium materials, 5-10% of carbonized corn straw powder, 5-10% of abandoned tobacco leaf dottle and 15-20% of water so as to obtain the fermentation raw material for standby application; (b) performing fermentation: uniformly mixing the following components in percentage by weight of 90-95% of the fermentation raw material obtained in the step (a) with 5-10% of a potassium degrading bacterium solution to obtain a mixed solution, adjusting the pH value of the mixed solution to 6.5-7.4 so as to obtain a fermentation solution, putting the fermentation solution into a fermentation tank, turning over fermentation materials once every 5.0-7.0 hours, controlling the temperature to be 35-45 DEG C, performing first-stage fermentation for 3-6 days, and performing second-stage fermentation for 7-9 days so as to obtain the slow-release potassium fertilizer containing microorganisms; and (c) appropriately reducing the temperature of the slow-release potassium fertilizer containing the microorganisms, which is obtained in the step (b), and performing grinding into particles so that the finished products of the slow-release potassium fertilizer containing the microorganisms can be obtained. Through the adoption of the preparation technology disclosed by the invention, the fertilizer efficiency can be prolonged for a long time, the drip washing of the potash fertilizer in soil can be avoided, and the requirements of cured tobacco at each growth period for potassium can also be met.