Advanced phase change materials (PCMs) are of vital significance regarding utilizing thermal energy from solar power for controllable and effective thermal management under variable-temperature environment. This study presents a graphene-modified hydrate salt/UV-curable polyurethane acrylate resin copolymer form-stable phase change composite (graphene-EHS/UVPUA), wherein the phase change temperature can be continuously regulated through influence of graphene on the entropy of system within the hydrate salt PCM. The results show that the phase change temperature decreases with a small increase of graphene addition in the hydrate salt. The modified mechanism of adjustable phase change temperature through the effect of graphene on the hydrate salt is characterized by Fourier transform infrared and Raman spectroscopy techniques based on chemical thermodynamics. Moreover, the solar-to-thermal conversion performance of the composite is investigated using an infrared thermal imager and the result suggests that the time, from the presupposed initial temperature (20 degrees C) to the terminal temperature (40 degrees C), taken for graphene-EHS/UVPUA with the addition of only 0.02 wt % graphene is reduced by 90.78%, compared to the control sample under the designed solar-to-thermal energy conversion measurements. The obtained results indicate that the graphene-EHS/UVPUA composites are promising for achieving adjustable phase change temperature targets of the hydrate salt PCMs used for smart thermal management.