In this paper, a metal-organic framework MOF-5 loaded polyethylene glycol (PEG) nanowire was used to form composite phase change material PEG/MOF-5. The molecular dynamics method was used to simulate the thermal conductivity, melting point and latent heat by G-K function and pseudo-supercritical path method, respectively. The results show that the pores of MOF-5 promote the increase of the angle of the PEG main chain and the extension of the helical segment. Therefore, the thermal conductivity of the composite (0.60 W/m·K) is 17.6% and 100% higher than that of the PEG nanowire (0.51 W/m∙K) and the skeleton (about 0.3 W/m∙K), respectively. At the same time, MOF-5 can improve the crystallinity of the PEG to a certain extent. The predicted latent heat of PEG/MOF-5 composite material is as high as 78.4 kJ/kg with a mass filling rate of 50%. This paper explores the mechanism from a microscopic perspective in order to provide models and data for the thermal design of such materials.