Hydroxy-terminated polybutadiene (HTPB) is one kind of polybutadiene chief chain structure polymer terminated with hydroxyl groups, because there are double-bonds in the chief chain, the α-hydrogen atom is very active, and crosslink reaction is easy to take place under γ-ray irradiation.,The property of HTPB is affected by γ-ray directly. So It is significant practically and theoretically to study the change in structure and property under radiation.,The microstructure of HTPB solute molecules and the change of molecular weight with radiation dose were studied by infrared spectra, NMR and GPC in our work. The effects of radiation on HTPB were discussed from the viewpoint of the change of solute molecular structure and gel kinetics. The measured gel dose of HTPB is 0.605 MGy, G=1.802, thus we can conclude the crosslink reaction is the chief process in the irradiation of HTPB.