In recent years, flexible-hydrogel wearable devices have undergone rapid development while photothermal therapy, energy storage/conversion, and other fields have been widely developed and used. However, the poor mechanical properties of hydrogels can affect their stability and reliability in practical applications, and it is often difficult to achieve both excellent mechanical properties and multifunctional characteristics. This study prepared a hierarchical cellulose network/PVA multifunctional composite hydrogel (MCPH) using cellulose nanofiber as fine fibers and microfibrillated cellulose as coarse fibers. The hierarchical cellulose network provides tensile strength as a skeleton while the PVA serves as the soft matrix to assist energy dissipation, which provides the composite hydrogel with good mechanical properties (toughness of 1.21 MJ m