Sweet Lime as a tropical fruit belongsto the genus citrus that is competitive in the global and regional markets, it is biologically active due to the high moisture content, Respiration, evapotrairation, ripening and other biochemical activities, cause a significant loss of quality and shorten its shelf life. Any substance with reducing the loss of water and biochemical activities of fruit as well, enhance shelf life. chitosan coating is an edible coating, with no negative impact on the environment and human health. This coating makes a kind of active packaging and prevents the growth of fungi and keep quality of the fruit apprance longer. In this study the effect of (0, 5.0, 1 and 2%) chitosan and a kind of commercial chitosan (Chitin Seal 901) on the shelf life of Sweet Lime fruit was studied. after keeping in cold storage at 14-11 ° C and relative humidity of 90% over a seven-month the fruits, were removed at intervals of once a month and then the firmness, weight loss, pH, titratable acid, soluble solids, flavor index, vitamin C, chlorophyll content and fruit rot were evaluated. The experiment was conducted through the split plot in time within a complete randomized design with 3 replications. The resuls of currently research showed that chitosan had a significant effect on all measured traits at one percent level of probability. The effect of time on all traits were significant. The Interaction between time and Chitosan were not significant in terms of firmness, titratable acid, vitamin C and soluble solids. Chitosan-treated fruit had firmness, vitamin C, titratable acids and chlorophyll more than those of control during cold storage. The pH of the extract, decay, weight loss and flavor index was significantly lower than control. The results showed that the highest firmness were observed with the fruit traited with commercial chitosan and 2% chitosa which demonstrated no significant, and the lowest firmness was recorded with cotrol. The highest percentage of weight loss were observed with cotrol and the lowest was recorded with those of the commercial chitosan and 2% chitosan. the highest TSS and organic acid were observed with fruits of 2% chitosan, and the lowest was recorded with the fruits of commercial chitosan. While the highest amount of vitamin C was recorded with the fruits treated commercial of chitosan and chitosan (2%). the lowest decay was observed with the fruits treated with chitosan (2%). According to the results of this study, it could be suggested that 2% chitosan increase the shelf life. Key Words : chitosan, postharvest, storage life, Sweet Lime.