The invention relates to a sustained-release oral ulcer film having biological adhesion and a preparation method of the sustained-release oral ulcer film. According to the formula, the sustained-release oral ulcer film having the biological adhesion consists of the following components in percentage by weight: 5-50% of a bio-adhesion material, 5-80% of a sustained-release film forming material, 0.5-10% of a medicine, 1-50% of a supporting agent, 1-20% of a plasticizer, 0.1-0.5% of a bacteriostatic agent and 0.5-1% of a flavoring agent. The film provided by the invention, which is prepared in a specific production mode, is good in stability, and excellent biological adhesion and sustained-release performance of the film can be kept for a long time; a soluble sustained-release gel can be gradually formed as the film is adhered to an ulcer surface and absorbs water, so that contact of the ulcer surface with external side is prevented; the oral ulcer film provided by the invention has the characteristics of diminishing inflammation, alleviating pain, achieving an antibacterial effect and being free from toxins, irritation, mutagenic action and the like; and the oral ulcer film can promote growth of blood vessel endothelium and proliferation of fibroblasts and keratinocytes, and subsequently, the oral ulcer film can promote regeneration, repair of healing of the ulcer surface.