This work was focused on investigating the effects of compounding conditions on the properties of fatty acids eutectic mixtures as phase change materials (PCMs), and the binary eutectic mixtures of stearic acid (SA) and myristic acid (MA) were selected as representative. The melting points of SA-MA mixtures with varying combination proportions were tested to determine eutectic ratio. Adopting heating-ultrasonic method, the SA-MA mixtures with eutectic ratio were blended under different conditions to obtain a series of eutectic mixtures, and then their thermal properties and chemical structures were analyzed by differential scanning calorimetry (DSC) and Fourier transform infrared (FT-IR), respectively. The results showed that the eutectic mass ratio of SA to MA was 36-64%; within certain time range, more heating time can result in lower melting point, but not the longer, the better; when the heating temperature increased, the melting point of eutectic mixture had a little irregular change, but the melting time of solid mixture obviously reduced, so, heating temperature should be considered synthetically to save energy; ultrasonic vibrating process hardly had influences on the properties of eutectic mixtures, and can be canceled; the preparation of fatty acids eutectic mixture did not have any damages to the chemical structures of fatty acids. (C) 2013 Elsevier Ltd. All rights reserved.