The invention relates to a chitosan contraceptive gel and a preparation method thereof. The contraceptive gel consists of 0.5 to 1.5 percent of chitosan, 0.5 to 1.5 percent of carbomer, 0.5 to 3.0 percent of triethanolamine, 10 to 30 percent of ethanol, 5 to 20 percent of propylene glycol, 0.3 to 1.0 percent of benzalkonium chloride, 0.5 to 2.0 percent of glycerin, 0.5 to 2 percent of citric acid, 0.5 to 2 percent of polyethylene glycol 400, 0.3 to 1.0 percent of benzalkonium bromide, 0.1 to 0.5 percent of ethylparaben, 0.1 to 0.5 percent of methylparaben and the balance of purified water. The preparation method comprises the following steps of: spraying the chitosan and the carbomer on the liquid surface of the purified water, standing for a whole night to form a gel substrate, and removing bubbles under vacuum after standing; and then uniformly mixing the triethanolamine, the ethanol, the propylene glycol, the benzalkonium chloride, the glycerin, the citric acid, the polyethylene glycol, the benzalkonium bromide and the ethylparaben, and gradually adding into the gel substrate for uniformly mixing to prepare the chitosan contraceptive gel. The contraceptive gel is used in the vagina of a woman, has the effects of contraception, antibacterium and lubrication, avoids the influences on the vaginal pH, and maintains the normal balance of vaginal microflora; and the contraceptive gel also has the advantages of the antibacterium, inflection prevention, no damage to a genital mucosa, small irritation, low allergy and the like.