The thermal degradation and kinetics of bisphenol A polysulfone (PSF) have been studied by high-resolution thermogravimetry (TG). The influence of the testing atmosphere and heating rate on the thermal degradation characteristics of the PSF has been discussed. The thermal degradation temperature of the PSF increases slightly with an increase of heating rate or with the variation of testing atmosphere in the order of: in air < in nitrogen < in vacuum < in argon. The activation energy of the thermal degradation for the PSF also increase from 140, 258 to 293 kJ/mol with variation of the testing atmosphere from air, nitrogen to argon. The activation energy of thermal degradation calculated by high-resolution TG in nitrogen and air are almost the same as those by traditional isothermal or constant heating rate TG. The isothermal weight loss in a certain temperature range could be correctly predicted on the basis of the kinetic parameters determined by nonisothermal high-resolution TG.