The evolution of structure, the changes of properties during the preoxidation, precarbonization, and carbonization of different polyacrylonitrile (PAN) precursors were firstly studied in detail by means of using hightemperature differential scanning calorimetry (DSQ to characterize with continuous heating from 25 to 1400 degrees C. It was essential to study the thermal behavior of PAN precursors so that proper temperature was determined. Three precursors with different composition, PI: acrylonitrile/itaconic acid (AN/IA) = 98/2 (wt/wt); P2: acrylonitrile/acrylamide (AN/AM) = 98/2 (wt/wt); P3: acrylonitrile /ammonium salt of itaconic acid (AN/AIA) = 98/2 (wt/wt) were, respectively, selected in this study. Comparative results of the DSC curves showed that the heating history influenced greatly the heat quantities released and exothermic position at low temperature of DSC curve, but influenced slightly at higher temperature. Aromatic index, carbon yield (W,) and weight loss (eta) can be calculated. After adjusting the temperature in preoxidation and precarbonization and carbonization technology depending on high-temperature DSC, the high performance carbon fibers were obtained that tensile strength is 3.56-4-.16 GPa, modulus is 235-243 GPa. (c) 2007 Wiley Periodicals, Inc.