The invention provides a method for preparing a selenium-rich crop cultivation matrix from bamboo biomass charcoal. The method is characterized by comprising the following successive steps: step 1, preparing bamboo biomass charcoal; step 2, preparing a selenium nutrient solution; step 3, preparing selenium-rich biochar: (1) preparation of heated selenium-rich biochar; (2) preparation of normal-temperature selenium-rich biochar; and (3) mixing of the heated selenium-rich biochar with the normal-temperature selenium-rich biochar so as to prepare the selenium-rich biochar; step 4, preparing a modified starch binder; step 5, preparing a selenium biochar granule; step 6, mixing the selenium-rich biochar with the selenium biochar granule and sending the obtained mixture into a granulator for granulation; and step 7, uniformly mixing particles prepared in the step 6 with a filling material for a soilless culture matrix of crops under stirring so as to obtain the selenium-rich crop cultivation matrix. The selenium-rich crop cultivation matrix prepared by using the method can improve the selenium absorption and conversion rate of crops and enables elemental selenium to be slowly and uniformly released in the whole growth period of the crops.