The invention belongs to the technical field of edible fungus production, and particularly relates to a pleurotus eryngii culture medium and a preparation method thereof. The invention is characterized in that the pleurotus eryngii culture medium comprises the following components in parts by weight: 10-20 parts of bran coat, 5-20 parts of cotton seed hull, 20-40 parts of peony seed husk, 10-20 parts of vinasse, 20-50 parts of Sesbania leaf, 1-4 parts of gypsum powder, 1-4 parts of sugar, 2-8 parts of animal manure, 5-15 parts of rice hull, 4-12 parts of corn cob, 5-15 acorn tree wood dust and 1-6 parts of acorn pulp. The pleurotus eryngii culture medium prepared by the method provided by the method is beneficial to growth of pleurotus eryngii, and has high biological efficiency for pleurotus eryngii (up to 109% or so). By adopting the Sesbania leaf which is a common plant in waste land and is often discarded, the method changes the waste into valuable substances, saves the resources, and reasonably utilizes the Sesbania leaf. The Sesbania leaf has high resistance to diseases and pests, and thus, is beneficial to preventing diseases and pests of the pleurotus eryngii and especially reducing the damage of mold mites and bacterium maggots to the pleurotus eryngii.