<p>The weak interfacial bonding and significant modulus mismatch between the reinforcement phase and the hydrogel matrix greatly limit the reinforcing efficiency in conventional composite hydrogels. To address these issues, we propose a novel design strategy based on dynamic mechanical control, summarized as “blending reinforcement in the viscoelastoplastic state and fixing the structure in the viscoelastic state.” This approach utilizes a unique poly(vinyl alcohol) (PVA) hydrogel matrix featuring an amorphous/strong hydrogen-bonding hierarchical architecture, which undergoes a thermal-induced transition from a viscoelastoplastic to a viscoelastic state, enabling effective filler dispersion and subsequent structural stabilization. The method effectively suppresses filler aggregation through mechanical mixing in the viscoelastoplastic matrix, while the high polymer chain density and abundant physical interactions reduce modulus mismatch between dual phases. This synergy, together with enhanced interfacial strength achieved through strong physical bonding and structural reorganization during the cooling-induced mechanical transition, creates a robust interface that promotes crack deflection and tortuous crack propagation. As a result, we successfully fabricate PVA/silica composite hydrogels with outstanding mechanical properties and long-term stability. Moreover, by leveraging the salt-responsive nature of the system, the mechanical properties of the composite hydrogels can be reversibly and broadly modulated <i>via</i> a salt solution exchange strategy. This work establishes a fundamental principle and a practical pathway for the design and fabrication of advanced hydrogel composites.</p>