Abstract: Chitosan can form a viscous solution by intramolecular and intermolecular hydrogen bonds, and the solution can salivate into a edible film with high transparency. Because chitosan film has certain mechanical properties, gas barrier properties and antibacterial properties, it has been widely used in food packaging to improve food quality. The mechanical properties, and water resistance of the pure chitosan film cannot meet the requirements of high protection and high moisture resistance of ideal packaging, which limit its application in food packaging. Actually, chitosan can often compound with other materials to improve its mechanical properties, barrier properties and fresh-keeping properties, and extend the shelf life of food. This article summarizes the preparation of chitosan, the film formation mechanism characteristics of pure chitosan film; and focuses that the amino and hydroxyl groups on chitosan molecules interact with the carbonyl, hydroxyl and acetyl groups on the polysaccharides(such as starch and pectin), proteins(such as gelatin), and antibacterial(such as glycerole, plant essential oils) through hydrogen bonds and ionic bonds, and forms a composite film with high tensile strength, good gas barrier properties, and strong antibacterial ability. It can provide the technical support of the development and application in chitosan composite film, and the food safety is improved, too.