The silica reinforced double-network structure hydrogels (alginate/polyacrylamide) were successfully prepared by one-pot synthesis technique in short time. The introduction of silica particles leads to the third interaction polymer-silica interaction in the hydrogels, besides covalent bonds and ionic bonds. A detailed comparison of the hydrogels with and without silica indicates that the incorporation of silica significantly increases the mechanical strength of the hydrogels (modulus and fracture stress), and keeps good elongation simultaneously, which can withstand high levels of deformation such as elongation and torsion, even can be made into a knot without damage. The mechanism is discussed based on the sacrificial bonds and the hidden length. (C) 2013 Elsevier B.V. All rights reserved.