Swelling properties and gel fraction of CMC hydrogels prepared by gamma radiation in presence of mono-and divalent salts (NaCl and CaCl 2) were studied. Two parameters such as effect of radiation dose and ionic strength of salts on the properties of hydrogel were observed. Swelling ratio and gel fraction of hydrogels depend on radiation dose and ionic strength of salts. Results also indicate that CMC with divalent salt, the gelation capacity is higher than that of mono-valent salt and swelling capacity of CMC hydrogel with mono-valent salt is higher than that of CMC hydrogel with di-valent salt. In addition, gel fraction increases and swelling ratio decreases with increased ionic strength of salt but at higher ionic strength < 0.41 M, an unexpected inversion of the trend is observed and gives low cross-linking value.