Phase change materials (PCMs) with storing and releasing energy properties have been widely used in lots of fields such as solar energy storing, smart housing, thermo-regulated fibers, and agricultural greenhouse. Here, PCMs based on polyamide 6 (PA6) blended with Polyethylene glycol (PEG) was studied. In order to improve the compatibility between PA6 and PEG, a PA6-PEG block copolymer was synthesized and added to the blends. The structure and properties of the block copolymer were determined by Fourier Transform Infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and optics microscope (OM). The results of DSC analysis showed that tThe copolymer block is phase separated. DSC results also showed that the phase transition temperature of the blend is different from that of pure PEG, indicating the interaction occurrence between PEG and PA6 by using PA6-PEG block copolymer, the latent heat of PEG/PA6 blend increased with the mass percent of PEG. The results of tThermal cycling tests showed that the blend as a PCM has good long-term thermal reliability.