Four precursors (mesophase pitch, condensed polynuclear aromatic resin, polyimide resin, and thermosetting phenolic resin) were heat treated at temperatures from 900 to 3000 A degrees C. These products were characterized by X-ray diffraction, transmission electron microscopy, and helium adsorption density instruments. Heterogeneous graphitization was observed above 2200 A degrees C in the resin carbons. Various constituents (amorphous, turbostratic, and graphitic) coexisted and transformed from being disordered to ordered with increasing treatment temperature. The molecular structures of the starting materials played important roles in the proportions of various constituents, crystallite sizes, and preferred orientation of the graphitic constituent of the different carbons during high temperature treatment. High-resolution transmission electron microscopy images showed that the structural features of Jenkins' and Shiraishi's model all existed in three resin carbons. Based on these results, we think that their structures are not belong to Jenkins' model, also do not belong to Shiraishi's model, are a complex of above two models.