The invention relates to a use of dimethyl silanol hyaluronate as a mucous membrane protective agent in preparation of a composition improving nasal mucosa and vaginal mucosa functions. The average molecular weight of the dimethyl silanol hyaluronate is 300-1800 kDa. The composition adopting the dimethyl silanol hyaluronate as a mucous membrane protective component and used for preparation of medicines for external use for mouths, nasal cavities and vaginas can effectively relieve irritation of external factors to mucosas, relieve mucosa function disorders caused by body factors, restore mucosa normal functions, and prevent and reduce occurrence of related diseases.