The surface thermodynamic properties of two types of cellulose-based carbon fibers (LYCF and RCF from lyocell and rayon precursors, respectively) were studied by inverse gas chromatography (IGC). It was found the molar free energy of adsorption (Delta G(m)(ads)) of n-alkane probe molecules on the LYCF surface is higher than that of RCF at different temperatures. The interaction of probes on the surfaces of LYCF and RCF becomes stronger with the increasing in the chain length of the n-alkane probes. Simultaneously, the ln K-s is linear to 1/T, where K-s and T are the constant of Henry's law and temperature, respectively. Similar results were obtained by using Dorris-Gray method (area per methylene unit) and measured probe areas. The results indicate that LYCF and RCF are different in the surface morphology and physical chemistry properties, which suggests that LYCF is a more promising cellulose-based carbon fiber material.