The invention discloses a polyethylene glycol/hydroxypropyl cellulose carbon nanotube composite solid-solid phase change material. The phase change material is prepared from polyethylene glycol (PEG),isocyanate (MDI) and hydroxypropyl cellulose (HPC) through a chemical grafting reaction. The phase change material is subjected to phase change at 80-120 DEG C, and after the temperature is kept for1-2 h, the stable solid state is still kept, and small molecule leakage is avoided; and the phase change process of the phase change material is solid-solid phase change, the phase change temperatureis 32-54 DEG C, the phase change enthalpy value is 99.5-130.8 J/g, and the thermal conductivity is 0.2494-0.5239 W/m. A preparation method of the phase change material comprises the following steps: (1) preparing an NCO-PEG prepolymer; 2) preparing a cross-linked polymer; and 3) preparing the composite phase change material. The preparation method has the following advantages: 1, the problem of leakage in the phase change process is solved; 2, the synthetic route is simple and has no pollution; 3, the phase change mateirla has good thermal energy storage characteristic and good thermal stability; and 4, the thermal conductivity of the phase change material is effectively improved, and the thermal conductivity is increased from 0.2494 W/m.K to 0.5239 W/m.K, and the utilization rate of heatis improved.