Abstract: Carbon foams were prepared without any curing agent using four kinds of commercial phenol-formaldehyde resins as raw carbonaceous precursors.To improve the self-foaming mechanism,relationship between physical and chemical properties of phenol-formaldehyde resin,foaming conditions and pore structure of carbon foam was investigated.Without curing agent, the decomposition and viscosity-temperature performance of phenol-formaldehyde resin during the foaming process are the main factors on its foaming behaviors.If the viscosity of phenol-formaldehyde resin is less than 2×10⁴ Pa·s during the foaming process,carbon foam with spherical and uniform pore structure can be obtained with pore diameter of 300~500 μm.Foaming pressure affects the cell density of carbon foam as well as its homogeneity of pore structure.