Polyurethane-based solid-solid phase change materials were first synthesized using polyethylene glycol (PEG) and hexamethylene diisocyanate biuret (HDIB), and the influence of halloysite nanotubes (HNTs) on this system was investigated. HNTs can not only serve as crosslinking agent in synergy with HDIB, which reinforces the solid-solid phase change properties of the system that has no leakage even at the temperature that 40 degrees C higher above the melting temperature of PEG, but also greatly improve the latent heat of the system from 86.8 to 118.7 J/g, as a result of heterogeneous nucleation effect, which can make up partial latent heat loss caused by crosslinking. Also, HNTs endows the system with excellent thermal stability, where the temperature at 5% weight loss is increased by 53 degrees C. The synthesized PCMs have extensive applying prospects in thermal energy storage fields.