The invention relates to a method for preparing a selenium-rich crop cultivation medium by utilizing fermentation residue biomass charcoal. The method is characterized by sequentially comprising the following steps: step 1, preparing the fermentation residue biomass charcoal; step 2, preparing a selenium nutritional solution; step 3, preparing selenium-rich biological charcoal: (1) preparing heated-state selenium-rich biological charcoal; (2) preparing normal-temperature selenium-rich biological charcoal; and (3) mixing the heated-state selenium-rich biological charcoal and the normal-temperature selenium-rich biological charcoal to obtain the selenium-rich biological charcoal; step 4, preparing a modified starch binding agent; step 5, preparing selenium biological charcoal particles; step 6, mixing the selenium-rich biological charcoal and the selenium biological charcoal particles, sending the mixture into a granulating machine, and granulating; and step 7, uniformly stirring granules obtained in the step 6 and a crop soilless cultivation medium filling material to obtain the selenium-rich crop cultivation medium. By adopting the selenium-rich cultivation medium prepared by the method, the absorption and conversion rate of crops on the selenium can be improved; and moreover, the selenium can be slowly and uniformly released in the whole growth period of the crops.