The polyethylene glycol/wood-flour (PEG/WF) composites were synthesized as novel form-stable phase change materials (PCMs) using PEG as phase change material and WF as supporting material. The composite products were investigated by Fourier-transform infrared spectrometer, scanning electron microscopy (SEM), the leakage test, X-ray diffraction (XRD), differential scanning calorimeter (DSC), accelerated thermal cycling testing and thermogravimetry analysis (TG), respectively. The results revealed that the maximum latent heats and encapsulation ratio of the synthesized PEG/WF composite form-stable PCMs can reach 90.9 J g-1 and 52.8%, respectively. SEM images demonstrated that the porous tubular-like channel spaces of WF are completely blocked by PEG. The thermal cycling test showed that the synthesized PEG/WF composite form-stable PCMs have superior thermal reliability after 200 melting and freezing cycles without leakage. Additionally, TG results revealed that the prepared PEG/WF composite form-stable PCMs have good thermal stability with the decomposition temperature higher than 200 °C. Thus, the novel PEG/WF composite form-stable PCMs are a promising candidate using in wallboard and building materials due to its excellent thermal properties and thermal reliability.