The invention relates to the technical field of biological antibacterial dressings, in particular to a medical biological antimicrobial dressing for a nasal cavity and an oral cavity and a preparation method of the medical biological antimicrobial dressing. The medical biological antimicrobial dressing is prepared from modified chitosan, camellia oil, peppermint oil, alums, olive oil, almond oil, a garlic extracting solution, a momordica grosvenori extracting solution, a licorice extract and anise oil. The medical biological antimicrobial dressing contains various raw materials with the effects of clearing heat, removing toxicity, relieving swelling and pain, cooling blood, stop bleeding, sterilizing, abandoning disease, resisting allergens, moistening skin and promoting granulation, and the raw materials supplement one another, so that the medical biological antimicrobial dressing can effectively inhibit and kill germs, relieve swelling and pain, stop bleeding, moisten skin and promote granulation, improve the environments in the nasal cavity and nasal sinus and the ventilation function of the nasal cavity, form an invisible protective film on the surface of a mucosa, effectively cure allergic rhinitis and chronic nasosinusitis, and prevent and treat oral diseases, particularly oral ulcer and gingivitis. The medical biological antimicrobial dressing has the characteristics of low cost, good curative effect and low possibility of recurrence.