A fluffy ultrathin-wall mesoporous surface carbon foam (UMSCF) with high thermal conductivity was prepared via carbon-thermal reduction reaction between a carbon foam and aluminium nitrate, and then used as a supporting material for stearic acid (SA) to form shape-stabilized composite phase change materials (PCMs). The UMSCF and the as-prepared SA/UMSCF composite PCMs were characterized by SEM, TEM, XRD, Raman, BET, FTIR, wettability test, compression test, TG, DSC, thermal cycling test and laser flash method, respectively. Results shows that the carbon-thermal reduction temperature greatly influences the microstructures of the UMSCF, and the UMSCF prepared at 1600 °C (UMSCF-1600) possesses good lipophilicity, high thermal conductivity and superior mechanical properties. The prepared UMSCF as supporting matrix simultaneously improves thermal conductivity and shapestabilization of PCMs, as well as retains relative high phase change enthalpy. The melting and freezing enthalpy for SA/UMSCF-1600 composite was measured as 149.3 and 151.2 J/g, respectively. The thermal conductivity of the composite PCMs is as high as 1.725 W/m K, which increases by about 6.791-fold compared with pristine SA. Meanwhile, the composites display good thermal reliability and chemical stability, suggesting their promising characteristics for thermal management applications.