As a natural edible alkalescent polysaccharide,chitosan have many advantages such as antibacterial,freshness,easy to form film and biodegradable. This paper summarizes the application of chitosan in keeping the freshness of food and gives an outline of its antibacterial properties and mechanism. Single usage of chitosan,modified chitosan and composite chitosan coating on fruits,vegetables and meat was described in detail. The effect of different factors such as concentrations and molecular weights on fruits,vegetables and meat was discussed. The mechanical properties of chitosan film and modified film was briefly introduced; the future development of fresh film of chitosan was proposed.