The invention relates to the technical field of antibacterial gel, in particular to chitosan antibacterial gel and a preparation method thereof. Each liter of the chitosan antibacterial gel comprises the following raw materials by weight: 5-30g of modified chitosan, 2.5-10g of carbomer, 1-1.8g of alum, 2-40g of glycerol, 0.3-10g of lactic acid, 0.1-0.8g of menthol and 2-8g of sodium carboxymethylcellulose. The chitosan antibacterial gel which is good in curative effect, can be used for preventing relapse of inflammation and is harmless to human body is prepared by using the synergistic effect of modified chitosan serving as a major raw material as well as carbomer, alum, glycerol, lactic acid and sodium carboxymethylcellulose serving as auxiliary materials, and is suitable for preventing, treating and nursing various vaginal bacterial infections, trichomonas infections, mixed infections, vulvitis, leucorrhea, candidal infection as well as wound infections of cervix uteri, genital tract and mucous membrane. By using the chitosan antibacterial gel, wound healing after physical treatment of cervical erosion is promoted, and nursing of vaginal dryness as well as cross infections in sexual intercourse and the like is improved.