Under normal circumstances，Lactobacillus are the dominant bacterial flora in human vagina. Lactobacillus adhere to the vaginal mucosa and produce a series of metabolites，they can protect us from HPV infection and cervical lesions. The mechanism is various，including inhibiting the colonization of pathogen，inducing body immunity，playing cytotoxic effects on cancer cells，performing antimutagenic effect，regulating carcinogen metabolism and protecting DNA from oxidative damage. In his review，we discussed the progression in the protective mechanism of Lactobacillus on cervical lesions.