A poly(vinyl alcohol)hydrogel was prepared by coupling puly(vinyl alcohol)with epichlorohydrin as cross—linking agent．The structure of the hydrogel was characterized by FTIR and GPC techniques．Various amounts of water were added into the dry gel to swell it and the quantity of water in various states in the partially swollen hydrngel were determined by differential scanning calorimeter technique．The analytical results indicate that the water introduced into the dry gel first combines with the hydrophilie groups of the network chains through hydrogen bond forming non—freezable water．The ratio of the non—freezable water to dry gel in the hydrogels is about 0．20．After the non—freezable water is saturated

the additional water penetrates into the network space and forms simultaneously both in the freezable and free water states until reaching equilibrium swelling．