Chitosan play an important role as an antifungal against Botrytis cinerea and the effect was a concentration dependent. The obtained results of in vitro experiment demonstrated that chitosan (4%) decreased radial growth of B. cinereato 2 %. Invivo the severity of infection reduced from 59.8 and 100.0 to 9.7, 33.8 and 40.1 in first, second and third week's storage periods at 13C, respectively. Also, chitosan coating (4%) significantly caused an increase in fruit firmness whereas TSS was decreased with an increase by increasing in storage time. However,Vitamin C gave fluctuated results by increasing storage time. Gamma irradiation at 2.5 KGy reduced severity (%) of infected fruits from 55.5, 100 and 100 to 31.7, 45.9 and 49.9 and in healthy fruits severity (%) reduced from 48.9, 100 and 100 to 23.3, 25.1 and 29.1 in different storage periods 1, 2 and 3 weeks, respectively. Similarly, chitosan as well as gamma irradiation combination induced a significant increase of peroxidase enzyme (POD) activity. Induced changes in surface morphology and damage of cell structure caused by using chitosan shown by scanning electron microscopy. Also, gamma irradiation causes changes in hyphea structure and in surface morphology but combination of gamma irradiation with chitosan was more effective in altering fungus morphology and cell structure damage and no spore forming. This providing the efficiency of combination on reducing disease severity (%) of strawberry.