The invention relates to a pleurotus geesteranus culture medium and a preparation method and application thereof. The pleurotus geesteranus culture medium is prepared from, by weight, 32-45% of hibiscus cannabinus side products, 32-48% of mixed saw dust, 5-15% of vegetable seed peel, 5-15% of bran and 1-3% of gypsum and lime, wherein the sum of the vegetable seed peel and the bran is 19-21%. The hibiscus cannabinus side products and the vegetable seed peel are matched for culture of pleurotus geesteranus, the problem of shortages of culture raw materials at present can be relieved, the edible fungus culture raw material source can be enriched, raw material localization is achieved, an industry chain is prolonged, the production cost is reduced, the economic benefits are improved, the economic income is increased for farmers, the problem of environment pollution caused by random abandonment or incineration of agricultural wastes can be avoided, and food safety can be ensured.