The influence of heat-treatment on microstructure, and thermal-conductivity of two-direction pitch-based-carbon-fiber with charred-resin-carbon matrix carbon-carbon composites was investigated. The heat-treatment was performed from 1800-to-2400°C in inert environment. The microstructure changes were determined by polarized-light-microscopy, XRD, Raman-spectroscopy. Polarized-light-images exhibited an opening of structure with pitch-fiber shrinking more than charred-resin-matrix. A modest increase in crystallite size was found from XRD patterns. However, Raman spectra showed a steady increase in the intensity of ‘Good’ band and decrease in ‘Defective’ band, indicating an overall increase in the crystallite size (La, Lc, d-spacing) and subsequent an overall increase in the order of the structure. Raman profiling of polished surfaces showed an evolution of more ordered structure with increasing heat-treatment-temperature (materials heat treated to 2400°C). In-plane and out-of-plane thermal conductivity of highest heat treated C/C was higher than the rest of the samples. An apparent correlation exists between increasing heat treatment temperature, microstructure and thermal conductivity.