The invention discloses a preparation method of an electromagnetic shielding biological material. The preparation method comprises the following steps: step 1, cutting moso bamboo into bamboo chips; step 2, soaking in a sodium hydroxide solution with the concentration of 20% for 2 hours; step 3, continuously soaking in a sodium hydroxide solution with the concentration of 3%-10% for 16-24 hours; step 4, crushing the bamboos by using a crusher, and then putting the crushed bamboos into a dry distillation kiln to prepare bamboo charcoal; step 5, after carbonization, mixing the prepared bamboo charcoal with an analytically pure ferric nitrate solution by adopting a vacuum pressure impregnation process to prepare a bamboo charcoal / ferric nitrate compound; and step 6, carrying out secondary carbonization on the bamboo charcoal / ferric nitrate compound, crushing, and screening to obtain the carbon powder. Bamboo blocks are selected to be processed into bamboo powder to prepare bamboo charcoal, so that the unit surface area is increased, the contact area with a hot gas medium in a dry distillation kiln is increased, the energy consumption is low, the production efficiency is high, the charring reaction is sufficient, and the final charcoal yield, the charcoal yield, the bamboo charcoal graphitization degree and the conductivity are improved.