The structure and properties of polysulfone under irradiation by gamma rays were investigated by mechanical testing, fourier transform infrared spectroscopy, scanning electronic micrograph, differential scanning calorimeter, gel permeation chromatography and X-ray photoelectron spectroscopy respectively. The results show that tensile strength, flexural strength, impact strength, number averaged molecular weight, peak molecular weight, glass transition temperatures and number averaged polymerization degree of polysulfone decrease with the absorbed dose. The chemical structure of polysulfone keeps unchanged. The embrittlement of material and the smoothness of the fracture surface increase with the absorbed dose. The ascending part of the aging curves of flexural strength, impact strength and weight averaged molecular weight of polysulfone reveale that the cross-linking mechanism dominates at lower absorbed doses, and descending part of the curves shows that degradation mechanism dominates at higher doses. Radiation degradation kinetics of polysulfone under gamma irradiation can be described as random event. It may be indirectly proved that cross-linking mechanism dominates at low absorbed doses, and degradation mechanism dominates at higher absorbed doses.