In this contribution, silver nanoparticle (AgNP) across the optimal 1D halloysite nanotube (HNT) hybrid nanostructure is successfully constructed via combining chemical reduction and self-assembly technique and then applied to prepare polyethylene glycol (PEG) based nanocomposite PCM (PEG/HNT@Ag) by a simple vacuum impregnation method. The nanocomposite PCM exhibits desirable phase change temperature of 33.6 degrees C, relatively high thermal energy storage density of 71.3 J/g, robust thermal reliability with respect to 2000 thermal cycling, as well as significantly enhanced thermal conductivity to 0.9 W/mK. Compared with pure PEG, the thermal conductivity of PEG/HNT@Ag nanocomposite PCM is increased by 2.08 times. Moreover, the nano composite PCM shows great improvement in the thermal energy storage/retrieval rates, which is ascribed to the successful construction of multiple thermally conductive pathways comprising a continuous 3D HNT framework decorated with high thermal conductivity AgNP. Therefore, considering the suitable phase change temperature, relatively large latent heat, excellent thermal reliability and enhanced thermal conductivity, the prepared PEG/HNT@Ag as an innovative form-stable nanocomposite PCM has great potential in thermal energy storage and conversion, for instance, as building materials to decrease the indoor temperature fluctuations, improve the indoor thermal comfort and save electric energy.