Double network(DN)hydrogels of poly(2-acrylamido-2-methylpropanesulfonic acid)(PAMPS)/ poly(acrylamide)modified by polyethylene oxide(PEO)were prepared using UV ray initiation polymerization.The structures of the first network hydrogels modified by different PEO solutions were observed with scanning electron microscopy(SEM).Compressive and tensile properties of the modified DN hydrogels and blank DN hydrogel were also determined.The result showed that many folds caused by PEO lamellae were irregularly distributed in the mesh walls of the first network hydrogels modified by PEO，and took part in the role of supporting mesh walls of the first network.When the molecular weight of PEO reached 50000，the supporting effect of folds was the best and mechanical properties of the DN hydrogels would reach a peak.As the amount of PEO increased，the mechanical properties of DN hydrogels were strengthened until the amount reached 0.1% then were weakened when the amount of PEO increased further. Lamellar structures of PEO chains reinforced the skeleton of the first network，which strengthened the compressive properties of DN gels to a maximum(31.6 MPa)，when the amount of PEO was 0.1%.However，further increase of PEO amount caused discontinuous structure of the first network，which resulted in a decline in the mechanical properties of DN hydrogels.