Abstract: The influence of heat treatment on the microstructure and mechanical properties of isotropic pyrolytic carbon prepared by chemical vapor deposition was studied by TEM, SEM, XRD, polarized light metallography, laser Raman spectroscopy, microhardness and threepoint bend tests. Results show that the interlayer spacing of the pyrolytic carbon decreases and the crystal size increases with increasing heat treatment temperature. At the same time, the microhardness and the elastic modulus decrease with increasing heat treatment temperature. Heat treatment below 2400℃ has no effect on the flexural strength of the isotropic pyrolytic carbon，but its flexural strength increases after graphitization at 2600℃. It is observed that the high temperature heat treatment has changed the pore structure, which consequently influences the mechanical properties.