The oxidation of C-60 solid was investigated using TGA, DTA, X-ray diffraction, FTIR, and optical microscopy. Oxidation reaction of solid C-60 commences at a temperature below 220 degrees C, resulting in the formation of a polycondensate (PCS) with C:O = 5:1. The associated heat of formation Delta H-f is determined to be 9.2 kJ/g. From the isothermal investigations carried out between 220 and 240 degrees C, the reaction mechanism is identified to be a two-dimensional nucleation and growth process. The PCS is found to undergo a structural modification without weight change beyond 220 degrees C with an enthalpy change of 4.6 kJ/g. The PCS itself is found to consist of (1) a glassy carbon with an inter-microfibril distance of 3.78 Angstrom obtained with the destruction of the C-60 cage, (2) an amorphous C-60-O-C-60 complex characterized by the intermolecular distance of 15.04 Angstrom with an oxygen atom forming a bridge between two C-60 molecules, and (3) an unidentified crystalline phase with carbonyl bonds.