One of the main limitations in the summer squash trade, preservation and its export is the short life after harvestand microbial spoilage will lead to a lot of waste. It can be used techniques after harvest to prevent the loss of quality characteristics and decay. Today the use of chemicals in postharvest is restricted in many countries and consumers prefer organic products and free of pesticide residues. Regarding increasing limitations, it should be used from other methods to prevent the quality features and its decay. It seems eddible coatings aregoodantibacterialresourcesto preserveagricultural crops. The current experiment was conducted to find the effect of chitosan eddiblecoating and its concentration on postharvest life (storage life and shelf life) of summer squash fruit cv. "Ezra". The first experiment was conducted to asess the age of storage life of summer squash using treatments of chitosan coating at 0, 5,10,20 g/Lit concentrations. After treatment, the fruits were presereved at an incubator with 10 °C and 90% RH for 25 days. After that the fruits were gotten out each 5 days and were asessed to determine parameters such as weight loss, firmness, soluble solids, pH, titratable acid, vitamin C, chlorophyll content and antioxidant enzymes (catalase, proxidase, ascorbic acid oxidase) evaluation.The second experiment was done similar to the first experiment for evaluating the shelf life except the fruit after treatment, were kept in an incubator with 18 °C and were tested at intervals of every 3 days. Both of experiments were performed as a split plot design in time in a complete randomized design with four replications.The results of the first experiment showed that chitosan treatments, have a significant effect on measured indexes except ascorbic acid oxidase enzyme.The results showed that The lowest weight loss,, soluble solids, pH, ascorbic acid oxidase enzyme and the highest firmness, titratable acid, vitamin C, chlorophyll, catalase and proxidase enzymes in the 2% (20 g/lit) chitosan were recorded Which it had significant different in measured indexes except catalase with other treatments except 1% treatment. The results of the first experiment showed that chitosan treatment significant difference in measured indexes except pH, chlorophyll b. The lowest weight loss,, soluble solids, pH, ascorbic acid oxidase enzyme and the highest firmness, titratable acid, vitamin C, chlorophyll, catalase and proxidase enzymes in the 2% (20 g/lit) chitosan were recorded which it had significant difference in measured indexes except treatment titratable acid and vitamin C with other treatments except 1% treatment. The effect of time on all measured indexes in both of experiments are significant. The interaction effect of treatment and time in the first experiment was significent at weight loss, firmness, pH, titratable acid and catalase and in the second experiment was significent at weight loss, titratable acid and total chlorophyll.According to the result of this study, treated fruits with chitosan 2% cause maintain fruit quality propertie during storage period. Keywords: Summer squash, chitosan, postharvest, storage life, shelf life.