In this work, a physically broken tough agar/poly(dimethylacrylamide) double network hydrogel was healed by a two-step process using silica nanoparticle solution and thermal treatment. Not only the shape of the hydrogel can be integrated again, but also its mechanical properties, and the healed hydrogel can achieve a very high recovery rate (64.1% of tensile strength) and the interface between two parts disappeared. This tough, mechanical-recoverable and shape-healable hydrogel is a suitable candidate for future tissue substitution due to its high mechanical properties and repairing mechanism.