The surface physical and chemical properties of T300-3K and T300-6K carbon fibers were characterized and the interfacial properties of these carbon fiber reinforced epoxy composites were also studied. Results indicated that the O/C ratio and active carbon ratio of T300-6K carbon fiber were higher than that of T300-3K carbon fiber. T300-3K fiber had the rougher surface while it grooves were lower, narrower and shorter than that of T300-6K carbon fiber. The interfacial shear strength (IFSS) of T300-3K and T300-6K carbon fiber reinforced epoxy composites were in the same range.