To describe the damage process of polymer in the energetic heavy-ion tracks by thermal spike model, polycarbonate foil (PC，Makrofol KG) stacks were irradiated with various swift heavy ions (1158GeVFe5656, 1755GeVXe13 6136 and 2636GeVU238238) in a very wide range of ele ctronic stopping power (from 19 to 171keV/nm) and the range of fluence fro m 1×101010 to 3×101212ions/cm22. The amorphization processes in the irradiated PC were studied by x-ray diffraction. By using the saturated track model (the damaging process only occur in the cyli ndrical track of area σ), the mean damage radii of tracks of the amorphization were calculated for Fe, Xe and U ion irradiation. The results obtained by using the thermal spike model, proved to be reasonable.