PVA hydrogels with different crystallinities obtained by varying freeze/thawed process cycles, as well as 2 hydroxyethyl methacrylate(HEMA) and 2 hydroxyethyl acrylate(HEA) hydrogels sheets crosslinked by polyethylene glycol dimethacrylate(PEGDMA 16) were prepared. The slide frictional properties of these hydrogels had been studied. It is found that the frictional behavior of these hydrogels do not obey Amontons law due to the hydrodynamic lubrication mechanism caused by the squeezed water from the surface of hydrogels. When the load increased, more free water is squeezed out from the surface of hydrogels, thus the frictional coefficient is decreased. When the PVA hydrogels are exposed to air, the evaporation of the free water on the surface of hydrogels causes the increase in the frictional coefficient of PVA hydrogels. Additionally, with the increase of crystallinity of PVA hydrogels or crosslinking density of HEA, HEMA hydrogels, the network lattice of hydrogels becomes smaller, the water is difficult to squeeze out, resulting in the increase of the frictional coefficient. PVA hydrogels with different crystallinities obtained by varying freeze / thawed process cycles, as well as 2 hydroxyethyl methacrylate (HEMA) and 2 hydroxyethyl acrylate (HEA) hydrogels sheets crosslinked by polyethylene glycol dimethacrylate (PEGDMA 16) were prepared. The slide frictional properties of these It is found that the frictional behavior of these hydrogels do not obey Amontons law due to the hydrodynamic lubrication mechanism caused by the squeezed water from the surface of hydrogels. When the load increased, more free water is squeezed out from the surface of hydrogels, thus the frictional coefficient is decreased. the, the evaporation of the free water on the surface of hydrogels causes the increase in the frictional coefficient of PVA hydrogels. crystallinity of PVA hydrogels or crosslinking density of HEA, HEMA hydrogels, the network lattice of hydrogels becomes s maller, the water is difficult to squeeze out, resulting in the increase of the frictional coefficient.