Abstract: The development of phase change materials (PCMs) with efficient photothermal conversion, rapid responsibility, and superior thermal management performance is important for effectively utilizing solar energy. In particular, designing flexible, rollable and foldable film PCMs can further expand the application of solar energy in portable and complex shaped structures. Herein, a synergistic approach combining the expansion and in-situ impregnation was used to integrate polyethylene glycol (PEG) into a continuous carbon nanotube (CNT) network, achieving a uniform CNT distribution and high PEG loading (97.2wt%). Thanks to the excellent photothermal conversion ability and high thermal conductivity of the CNT network, the film was able to efficiently capture and rapidly realize the photothermal conversion, heat transfer and uniform heat distribution, and exhibited high thermal storage capacity (146.3 J·g⁻¹) and photothermal conversion performance (67.8%). Under the environment of −10~40 ℃, the film showed good thermal regulation performance with excellent flexibility and good thermal stability. In addition, this paper discusses the key factors affecting the thermal management effect, which provided new ideas for the development and application of flexible thermal management materials.