Summary Sugar alcohols are promising solid‐liquid phase change materials (PCMs). However, problems such as possible leakage of liquid PCMs, high and unstable supercooling, and low thermal conductivity need to be solved. In this work, a novel form‐stable PCM in which m‐erythritol (ME), polyaniline (PANI), and silver nanowires (Ag NWs) were applied as solid‐liquid PCM, supporting material, and thermal conductive filler, respectively, was successfully prepared in anhydrous ethanol by surface polymerization of aniline. Form‐stable PCM with good form stability could be obtained when the ratio of ME/(aniline + ME) was no more than 78.7 wt%. The melting enthalpy (ΔHm) of the ME/PANI form‐stable PCMs could attain 234.8 J/g while that of the ME/PANI/Ag NWs form‐stable PCMs was about 220 J/g. In addition, the thermal conductivity of the form‐stable PCM was increased by 61.6% when 7.5 wt% Ag NW was added. Moreover, the supercooling of ME was effectively suppressed from 100°C for pure ME to 60°C, corresponding to an improvement of 40%, for the form‐stable PCM containing 7.5 wt% Ag NWs. The supercooling suppression could be ascribed to that PANI provided great amounts of nucleating centers and improved the nucleation kinetics, and Ag NWs improved the thermal diffusivity and thus increased the crystallization rate.