Capric acid-hexadecanol (CA-H) and capric acid-paraffin section (CA-PS) composite phase change materials were prepared by a melting-blending method, and two new composite phase change energy storage materials based on expanded graphite were obtained by the physical adsorption method. The results showed that the optimum mass ratio of CA-H and CA-PS were 74:26 and 81:19, respectively. It was found via FT-IR that CA, H, and PS acted together by molecular force without chemical reaction. The phase transition temperature of CA-H and CA-PS was 24.22 and 26.99 degrees C, respectively, and the latent heat of phase transition was 190.5 and 153.7 J/g, respectively. On the other hand, the best mass ratio of CA-H/EG and CA-PS/EG was 11:1 and 7:1, respectively. On the basis of SEM and FT-IR results, it was found that CA-H and CA-PS were uniformly distributed in the pores of EG by physical action; the melting and freezing temperatures are in the range of 21 similar to 28 degrees C, and the latent heat was in the range of 133 similar to 178 J/g by DSC. CA-H/EG and CA-PS/EG had good thermal and chemical stability after 1000 accelerated melting-freezing cycling tests. According to the TG and thermal storage experiments, CA-H/EG and CA-PS/EG had excellent heat resistance, and the high thermal conductivity of EG promoted the thermal storage and release rate of CA-H and CA-PS. Therefore, CA-H/EG and CA-PS/EG can be used as candidate materials in the fields of building energy savings.