With stearic acid (SA) as phase change material, waste polyacrylonitrile fiber (PAN) as framework material, N,N-dimethylformamide (DMF) as solvent, form-stable PAN/SA blends phase change materials (PCM) are prepared by solution blending process. Phase change temperature and latent heat and the thermal stability of the PAN/SA PCM are characterized using Differential Scanning Calorimetry (DSC). The structure, crystalline morphology, and thermal insulation properties of the PAN/SA PCMs are investigated using Fourier transformation infrared spectroscope (FTIR), polarizing optical microscopy (POM), and temperature-recording instrument. The FTIR and POM results show that PAN and SA are combined by intermolecular forces, and SA is homogeneous distribution in the PAN matrix. The DSC results indicate that PAN/SA PCMs have high latent heat storage capacity of more than 115J/g, the phase transition temperature and phase transition enthalpy of the PCMs increase with increasing the mass percent of SA. Cooling curve of PAN/SA PCMs show that the PCMs have good insulation properties, the soaking time is continued for about six minutes, and the thermal insulation properties remain unchanged after five and ten times of thermal cycling. The best process condition is obtained by the soaking time and orthogonal experiment.