Hydrogels are cross-linked polymers suitable for various applications,but the thermal conductivities of hydrogel-based composites have not been thoroughly investigated.In this study,agarose hydrogel-based composites with various boron nitride (BN) fillers were synthesized and their thermal conductivities were systematically investigated.With the increase in the agarose content from 1.5 wt％ to 3.0 wt％,the thermal conductivity of the composite decreased.The composites with BN micropowder had larger thermal conductivities than those of the composites with BN nanopowder at the same filler loading,as the BN micropowder provided better thermal conduction pathways in the hydrogel matrix than those provided by the nanopowder.The maximum thermal conductivity of 2.69 W·m-1·K-1 was achieved when 15 wt％ microscale BN fillers were added into 1.5 wt％ agarose hydrogel,which was 3.5 times larger than that of the pure agarose hydrogel.Additionally,a theoretical model was used to calculate the thermal conductivities of the BN/agarose hydrogel composites;a good agreement was achieved between the experimental and fitting ones.This study demonstrated that the thermal conductivities of hydrogel-based materials can be efficiently and significantly enhanced using BN fillers.