Radiation induced crosslinked polysulfone was studied by means of Pyrolysis Gas Chromatography (PGC). We suggested the possible crosslinking sites of polysulfone according to the change of the relative content of pyrolytic products with the radiation dose. The gelation doses of the polysulfone crosslinked at different temperature were obtained from the relationship of peak height ratio of benzene: toluene in pyrolytic spectra to radiation dose which were quite consistent with the value obtained from other method.