A new capric acid (CA)-modified vermiculite composite phase change material (PCM) with improved adsorption ability and enhanced thermal stability was prepared in the present research. The silanization vermiculite (SV) obtained by two-step acidification and silanization treatment was used as the CA-supporting matrix. The differential scanning calorimeter detected the fusion enthalpy of CA-SV composite as 118.41J/g, which was 37.1% higher than that of CA-expanded vermiculite (EV). The phase conversion rate ()-temperature (T) curves and the d/dT- curves revealed that the phase transition hysteresis phenomenon of the CA-SV composite was more conspicuous than that of CA-EV. It was also found that the fusion enthalpy loss of CA-SV was 3.1% after 1000 thermal cycles. Therefore, it can be concluded that the CA-SV composite PCM with enhanced containment ability and improved thermal stability is a promising candidate for thermal energy storage applications.